Hi. Well typically most keyboardists record their key tracks into a sequencer and then render to audio at mix time. But if you like to record directly to audio, that can work too. As for the nice rich enhanced sound, that's generally a product of the gear which comes between your keyboard and recorder rather than the recorder itself. But anyhow for keyboard it really depends on what you're doing. For example if you want a really rich grand piano sound your best bet is to play into a PC hosting any of the popular VSTis in the genre such as Akoustik Piano, Bardstown 24 bit Bosendorfer, etc. For strings a lot of people like Garritan Orchestra, for Hammond they use NI b4, for Rhodes-- Elektrik Piano. And so forth, and that's not even covering synths yet. So there's no single setup which works well for everything but basically the gist is that when you use a sampler you can leverage the "richness" of the professionally captured sounds rather than trying to create them from scratch in your environment, which is probably going to be much more effective/feasible.

You mentioned bass? Trilogy bass by Spectrasonics is the best overall keyboard bass module I've ever heard, bar none. Listen to the samples:
http://www.spectrasonics.net/instruments/trilogy/demos.html

Anyhow my best advice is to take the plunge with PC recording as soon as you can, for a keyboard player that's the real Disneyland. Standalone recorders can do quite well also but they tend to be much more limited. Being on a PC allows you to take advantage of all the free stuff on the net (tons) as well as all the new stuff, etc...

Anyhow I hope that helps. 8-)

Since you didn't go into any details about how you tracked the music from your keyboard it's a little tough to give advice. However, here goes:

Calgary gave you some good advice. Don't just run the entire sequence out of the stereo outs. Track each instrument separately. There are many inexpensive and even a few decent free DAWs out there for Mac and PC. This allows greater control of FX, EQ, panning, automation, etc.

Korg tends to be "thin" to my ears. Try some other sound modules or soft synths for more variety in your sound pallatte.

Don't over quantize; you'll crush the life out of your tracks.

Good luck and have fun.

A former partner of mine worked a midi-based room primarily driven by Korg products. 'Thin' was never an issue. Though we did sequence many key parts, we always went with separate outs to the recorder. And this was through a console. I could list the gear but here I feel its unimportant as the point is to get all the pieces of the arrangement onto separate tracks. Its here in a mix, they can be manipulated to a deeper and more complete sound than what the left/right outputs of the stereo sequencer can provide.

I agree, Korgs are not necessarily thin sounding. Here's a scratch piano track I played live from an 01W/FD through the direct outs using the stock piano patch. The recording itself is atrocious, I was just basically scrambling to get some ideas while writing tunes, but the main thing is that you can hear the Korg 01W at least is definitely not suffering from thinness. :)

http://216.234.180.26/piano.mp3