steve,I was using a Media Magic sound card at first, then i got a Yamaha OPL3 for my birthday. WHAT A DIFFERENCE!! The piano sound even almost sounds like a piano!
If you can afford it, I would recommend changing your sound card 1st. I don't know enough about them to recommend one to you, but I like my Yamaha. I'm sure there are better ones, depends I guess, on how good you need it to be, ie professional, or just so it sounds better for your ears only.
Good luck.
paul