Don't Do It!
The D20 is basically a simplified D50 with a sequencer. It's quite basic, 16 note poly and you will find better sounds these days on your average computer soundcard. If you are looking for a cheap 2nd hand synth, go for a Korg X5 or Alesis QS6. You should pick one of these up dirt cheap, they have 64 note polyphony, some useable sounds and you won't run out of ideas nearly so quickly...!