There is nothing wrong with the microkorg, and lots of people do interesting stuff on it...but of all the synths i've had and played, i never regretted selling it and I found its limitations (tiny keys, 4 notes at a time) too much to keep it.

X-station, xiosynth, mini-AK/micron, + tons of other choices out there.
Keep an eye on ebay/craigslist/check out the site roguemusic.com used gear (or guitarcenter) for ideas.

Vintagesynth.com/forum has endless talk about synths, and synthmania has good sound clips

Good luck, find what really inspires you

If you're not worried about keys, I've drooled over the SH32. It's cheap, has mini sequencer on it. Only thing I've heard people complain about is the stairstep knob turning, but when LFO is involved it's smooth sailing. And it's Roland if you're a brand devotee. I've seen them as low as 120$. Again, drawback is no keyboard. It's just a sound box you gotta play with.

SH32 is great, had one and sold it, regret it somewhat but I had too much gear. Very nice sonic complement to the SPs because it can get nasty (bit reduction/crusher) but also has decent delays and other effects...plus its like 32 voice at once I think? (vs. Microkorg...4)..and multitibral so you can have it doing 4 parts (bass/lead/pad/fx) or whatever.

I have a love/hate relationship with my Microkorg.

Sometimes it can sound lush, other time's it just sounds like ass. 4 note polyphony is whack! it's a pain to program, editors can help tho. Damn minikeys too! But I love the portability and size of it.

If I want to play real size keys, I got my DX7 for that