I just went through a big keyboard purchase myself! If I were in your position, depending on how I felt about the Planet Phatt, I'd either keep it (if I found it indispensable for my work) or possibly trade it for the new "phatt" module (if you feel you need to "update" your sound). Having two modules from the same company, that do basically the "same" thing can lead to a pretty "homogeneous" sound. I'd go for the Karma because if nothing else, it'll give you some different colors.
Personally, I was trying to decide between the Mo Phatt, the Korg Triton, and the Roland XV-3080 (I do mainly pop/R&B stuff, but some other things as well). I didn't really look at the Motif because I've never much liked the user interface on any Yamaha gear I've owned or used, although everyone I've talked to that uses it thinks it's great. I ruled out the Mo Phatt first because I knew I would burn out on it quickly. Too much of one thing IMO. I really couldn't decide between the Triton and XV-3080. I LOVE the sound of the Triton. Big, fat, warm, clear and exciting. A few too many pad sounds for my liking, but awesome sounding. The XV-3080 didn't excite me at all in the store, but seemed to have an awful lot of range. I bought both and left the store thinking the Triton would be my main thing and the Roland would fill in the holes. I've since put the "Vintage Synth", "Techno", "Hip Hop" and "Special FX" JV-series cards into the XV-3080 and I've got to tell you, that Roland module is AWESOME. Probably the best overall piece of keyboard gear I've ever purchased (and I've got a room full of keyboards over here including a lot of the "classics"). And contrary to what I thought, I use the Roland for EVERYTHING (leads, basses, pads, pianos, drums - everything) and the Triton to fill in the holes!
Bottom line is, you can't go wrong with the Korg Karma (same sounds as the Triton). My Triton is amazing - wouldn't want to work without it. But just to confuse matters even more, maybe you might want to check out the XV-3080 with a couple of the cards? Hope this helps.
Brent