Just to pick up on a comment that John made, it should be remembered that MIDI is only a set of instructions to a synthesiser (in most cases a sound card) and to get the best out of MIDI, rather than having it sounding "computer generated", you do need something which provides decent wave table synthesis. I know nothing about the software solutions that John mentioned although I would imagine they are quite processor intensive. My sound card is only a Sound Blaster AWE32 but I do have the Yamaha DBXG50 daughter board attached. It may be old but for MIDI, it transforms the soundcard and provides a quality of sound comparable with some of the Yamaha PSR range of keyboards.

Also, on sound, I dont use PC speakers but hook up (line out on sound card to aux in) to my Kenwood amp and apart from getting me good quality sound, this provides me with a very effective means of recording to tape.

Jon