Answering a couple of questions above:
The Ensoniq and SB16 PCI are the same card. Creative bought the design out from Ensoniq and then raised the price. Creative, in truth, hasn't engineered anything original for quite a while--they also bought the SBLive EMU chipset. (Dunno about the new Audigy cards.)
And both the Ensoniq and SB16 PCI have been measured with quite excellent specifications--on the order of a frequency response from 20-20,000 Hz +/- 0.1 dB. For stereo playback, they are still all that you need. For the guy with the bad-sounding Ensoniq card--you have a defective one, or a bad interface with you system bus. "Back in the day," meaning just a few years ago, the SB16 PCI was used as the basis for some serious and expensive data acquisition software systems ($500 and up) because it had the best measured performance of any card on the market.
For games, of course, you want a card with multichannel and 3d-sound API support, and the SBLive is still a good choice, maybe the best economical choice around.