Scott,
theoretically the Yamaha SW1000XG card can provide what you need. you can buy one used fairly cheap, the card had some raving reviews and won "best card" or something for 4-5 years in a row. Has 20 MB of wave ROM, built in effects, doesn't take processor time, blah blah. If you search on the net you'll find many reviews.
But as Pro said, it is obsolete, and there is a chance it may not work with your particular Pc chipset. take a look at www.xgfactory.com for info. It is a $100 bet.
Another way would be Hypercanvas. sounds ok for me, and check the posts by Frank Rosenthal, rikkisbears and Starkeeper and download Another XG soundfont. they say it sounds good enough for styles and you can use it on a regular Creative card.