Zuki, you might try T-Racks as a mastering program. Inexpensive, but with all the basic tools. Yes, it's not as good as some of the REALLY high end stuff (I use a suite of UAD-1 mastering plugins and some Waves stuff for most of my plug-in mastering, it compares fairly well to the studio's Manley Massive Passive, Slam and hardware L2, IMO), but used carefully, it can do wonders.

The host software is usually not as important as which plug-ins you use, most native DAW's don't include as high quality mastering plug-ins as a dedicated package...

Then finally, if the Korg can do it, I would recommend recording as a .wav file, preferably 24 bit (but 44.1kHz is fine) if you are going to master it. You will get a FAR better result encoding to MP3 after the mastering, not before. If the Korg is limited to MP3 only, you might get a better sound with a modest soundcard in the computer and record at 24/44, or even a Zoom H2 or the like. Once you convert to MP3, you lose sound quality you can never get back. Do it last, and the mastering software is at least working on the best possible source...

Hope this helps...

Just noticed you are going to CD... OK, forget about the MP3 encoding completely. 24 bit .wav is the way to go, and master to 16 bit .wav (with dithering on) as the final process.

I do mastering work for many local artists, and some pre-release mastering for major label artists, so if you need further advice, feel free to contact me.

Thanks Diki. I'll experiment a bit and let you know.