May I suggest the Ensoniq Audio PCI sound card.  It is a PCI wave
table sound card.  It is not as good sounding as some, but much better
than the standard sound cards.  Being PCI it is not a resource hog,
and it doesn't require much processor use time.

I got one at a computer show for less than $40.  It is used in
parallel with my Casio CTK 601 keyboard/synthesizer.  They both have
reverb available, and they don't sound half bad.  Best to all of you.

Jim Cook