I think these are the best ‘low cost’ monitors out there. They’re more money than the Mackie’s, but they are a monitor that truly gets the job done. I think the mackies are gonna give you a hard time making mix judgements.

https://www.amazon.com/dp/B00CFOX420/?tag=r06fa-20

I second the HS5's K.
I mix in far less than ideal spaces at times and they remain consistent and something I can count on. Perhaps it's because I've "learned" them? I think that once you get it about the lows (I've cross-checked them enough with my JBL bigs) they work real well.

Don't ignore the acoustics of your room. No monitor can perform at its optimum if your room has sonic issues. Treatment can really help you to mix things more accurately. You should do an acoustic measurement of your room. See what's happening over the frequency range. Then apply treatment as necessary to counter certain problem frequencies. It will also help your recordings, if you are recording in the same room.

As an addendum, you'll need a good small diaphragm Omni condenser mic designed for measurement purposes. You don't want a mic that has any inherent "character" or color, and you will need measurement software to analyze the response of your room.
REW is a good program, and it's free. ( You'll have to buy the mic, though):

https://www.roomeqwizard.com