Hi!
Just to clarify: if you want to burn your songs to CD you will have to record the actual sound coming from your MPC's audio outputs (not the MIDI connectors) into your computer thru your soundcard's audio inputs. Depending on the software and the soundcard, this can be anything from a straight stereo recording of your chosen song, to a multi-track recording of individual tracks (say, drums on one track, bass on another and so on).
If all you want is your finished songs on audio CDs, then you just record the stereo signal coming from your MPC to your computer using the appropriate software, and then burn your CD. As such, any soundcard will do the job, however, a better quality soundcard will yield better end results.
In case you didn't know: MIDI is just a communications standard between electronic music instruments and gear, it does not actually transfer any sound within its leads. Are we confused yet?
Good luck!
Arne S.