Your post is leaving out a lot of info needed to give you a helpful response...

For example, what mic pre are you using? What is your recording platform? If you are using a DAW, what audio I/O are you using?

Whether or not you downgraded is all relative... I've heard fantastic tracks recorded using nothing more than a $99 Shure SM57/58 mic.

Another suggestion would be for you to describe the gear you are using, past that of just model numbers. I was a professional engineer for over thirty years, and off the top of my head, I have no idea what an Art TPS or Rane MS1 even is by just reading a model number.

Be more specific about the gear you are using and what you want to accomplish, and you'll get more help.

"...For example, what mic pre are you using?"
He said that it was the Rane. And that litle MS-1 is a sleeper...it is clean and very transparent with good detail. 3 things the TPS is not, so no worries there. The TPS is a poorer build quality with over-hyped, under-fed tubes. That "voicing" selector is famous for crapping out, and the box is noisey. The Rane is a higher-quality, rugged, made-in-the-USA product.
You don't mention WHAT you are recording and WHERE this will happen.
I have used the CAD e100 in church and I own a pair of KSM27's. The CADs suffered from too much off-axis coloration in a live room when used on a choir, and they were downright harsh on a Kawai 6-ft grand. The 27's, by comparison, were much more detailed and more natural sounding on the same piano. I like the "KSM sound" - which is actually the absence of bad sound - on a lot of instruments. I would tend towards a good old SM58 for a lot of vocals, though.
Your gear is not the fault here, you need to be cognizant of the recording acoustics and how to use that and the mic to work with your source(s).

Not a "downgrade" by any stretch of the imagination and for the exact reasons Mooney spoke of. The KSM27 is a nice neutral mic with plenty of gain.

I think you've downgraded. If ya can't make a good recording with any SHURE microphone, you've downgraded your skills LOL.

Downgrading, upgrading, it just comes down to good engineering technique and not someone's piece of professional equipment not quite up to your standards. As a professional engineer for over 40 years, you don't always get your choice of equipment to use. It just has to be functional for you to do your job. Not sounding good? Then it's you and not the equipment. I'm not saying you're a terrible engineer, you're obviously still on the long learning curve.

In fact those SHURE studio condenser microphones, output a very hot level. Lower? No way. So this reeks of operator error, sorry to say. And yeah, most of those great studio recordings are mostly $100 SM-57's or a 58 with no balls, or so to speak LOL. You're on the ball with that 58, when recording vocals and incorporating an additional foam pop filter. And that stuff sounds great because they don't sound like condenser microphones. Condenser microphones are highly overrated. And too many folks think that's what you'd need to use almost exclusively, in the studio and it's not.

So if that KSM-27 doesn't sound good, you're pointing in the wrong direction most likely? Ya know the sound is picked up at a right angle to its long body? A.k.a. side address. Don't feel bad if you made that error. Plenty of people have. You wouldn't be the first.

Really just set the gain trims properly.
Mx. Remy Ann David

I have a KSM27 here and it has plenty of good hot level, so I would say some is wrong elsewhere?
As for the KSM27, I am really not a big fan but I keep it around. No love for the cad mics I have had a few and although I rarely part with gear those thing where out of here as fast as I could get them on ebay!
Find out what the issue is and grab some SM-57's or 58's maybe a Audix OM-2 or something along those lines.
I will take a well designed dynamic that has proven it worth year after year over a cheap condenser anyway. Don't get me wrong I do love my condensers and have a number of them but dynamic just rock!
I had my lawson out for some vocal recently and my RE-16 just did the job and got what I wanted, and the Lawson aint no slouch, not by a long shot.

Plenty of mega hit folks, have tracked the lead vocals through SM58's & SM-7's like Steve Tyler, Bono, Michael Jackson. And if it's good enough for their hits, it's good enough for your hits. Sure, much of the time you'll find someone's large diaphragm condenser microphone, lead vocals but certainly not always. So when you're not getting the vocal that you want from a condenser microphone, just grab a 58. And your life will be changed instantly. Then you can still add as much compression/limiting/EQ, as you see fit. The more the merrier I say.

Simona says use a 58. And you've got to do what Simona says.
Mx. Remy Ann David

+1 on the pointing the mic the right way. That was my first thought when the OP cited such stark differences in sound, on a nice mic. lol, i actually did that in a session a couple weeks ago. i put up a akg c3000 and it us a bit dull (not usually an akg mics characteristic), and i heard this litlle delay, and we use direct monitoring. so after checking the auxes, and connections, i figured out the mic was pointed at the booth window about a foot away. after that the mic sounded fantastic, and beat out the 87. took me 12 years to make the mistake, but now i know right? :)

Plenty of mega hit folks, have tracked the lead vocals through SM58's & SM-7's like Steve Tyler, Bono, Michael Jackson.

If memory serves correct, I recall hearing a blurb on the audio grapevine a few years back that Bono used a 58 as his primary mic on Achtung Baby. Might be an audio myth, but it wouldn't surprise me if it were true.
Also heard somewhere that the Red Hot Chili Peppers used 57/58's as the primary vocal mics on Californication. Of course, in both of these cases, to be fair, we would also need to consider the very real possibility that they were also very likely using fantastic pre's - or other front load processors that were of very high quality... but that still doesn't detract from the 58's quality and performance out of the box and on its own.

Personally, I remember a session once, run of the mill pop/rock, where we started the vocalist out on a U89i, bused through an Avalon Mic Pre on the front end. Still not entirely happy with it, we moved him to a 414.
Still not getting it, we finally put up a 58...

Bingo. Instant tone for that vocalist.

Which brings up the point to consider that there is no such thing as one "end all/be all" microphone. Voices differ so much, not just in timbre, but in resonance, in sibilance, in texture, and even the same person's voice can change greatly from day to day... so it's best, if you can afford it, to have a variety of dynamics, condensers, and ribbons in your mic locker.

But, for the price of a tank of gas, a pack of cigs, a six pack of beer and a box of donuts, you could pretty much buy a new-to-nearly new 58, which is as good of an all round mic as you're going to get... and not just in it's price class, but stacked against many other expensive mics as well. It's the only mic, along with its cousin, the 57, that you can mic a snare, kick, guitar amp, bass amp, brass, vocals, even acoustic guitar ( yes, I said acoustic guitar), then use it to hammer in roofing nails and still go do a live gig with it. ;)

If I had to go to desert island with only one mic, it'd be a toss up between a Shure SM57/58 and an EV RE20... and a tough decision it would be indeed... and that's coming from a guy who has U87's, U89's, 414's and other good mics in his locker.

IMHO of course. ;)

another bonus with the 58 is that most singers are familiar with it, and know how to work it (and I'm not just talking "sing into the mic"). A good singer using the characteristics of a mic well can help the mic sound better.