It's hard to beat $7.50 for something you plan to use with headphones - are you planning to use PC speakers, or do you have something with a digital input, because then it really shouldn't matter much.
For really basic sound, I've found no problems with even cheap onboard sound for the last few years.
For something with a little more in the way of features, my SB Live Value has been fine, and I'd imagine the newer ones probably have 5.1 analog outputs for a pretty reasonable price.