korg doesn't make them anymore so you can only get them second hand, but if you can find one for about 300-400 then you're golden! the km402 is your four channel variant and km202 is the 2 channel.

separate post-fader fx for each channel, which is primarily what you're looking for I think. I had the same problem with a kp3 muddying up my sound (my 4-channel didn't have send/return) until I decided to bite the bullet and get one of those.

only drawback is that you're stuck with the miniKP fx, but most of the good ones from the kp3 are on the miniKP anyway, and unless you're planning on doing crazy sampling/looping/etc, the kp3 and the miniKP are roughly similar

If your mixer has an fx send and return, I'd put the KP3 there, so you can send all sorts of stuff into it.

You're right. It was really bugging me, after i bought the KP3, that i have to pick which devices to run through it ahead of time, and that the FX gets applied to all of them. This would solve that problem.... so i guess i need to buy a new mixer.

Sounds like you've got it down pretty solid tbh! Don't be afraid to start with simple rigs and expand on them later. It's much safer than attempting a live rig with a ton of crap that just might die on ya

Thanks! It's hard to resist the urge to plug everything into everything. What I did noticed is, I got a lot more accomplished in a shorter time with the smaller rig. That's good because I'm going to try to make one new tune every week, and that usually means one afternoon, on the weekend.

The setup:
NSF (from computer until my Powerpak arrives) --> KP3 --> 4 ch Mixer
Alesis SR18 (drum machine) --> 4 ch Mixer
4 ch Mixer --> PA ( or digital recorder when practicing)

Here is my first song with this setup, i guess it is a proof of concept.
https://soundcloud.com/scripterio/sunday-morning

Other gear:
3ds with KorgM01d
DSiXL with Korg DS-10+
Modded DS that can play roms ( GB / NES / NDS (ds-10)
Gemini 2 Channel mixer