Stay away from Turtle Beach's new cards, they get horrible reviews. esp. the Riviera.
The Santa Cruz they made at the turn of the century is good, but if you're doing more then gaming, like recording, or a home theater in a box setup, you'll want something better.
Absolute trick is not buying any brand new (2009) sound card. You can get excellent cards from '08 and earlier for not too much. M-Audio is an excellent brand, I advise visiting Hydrogenaudio's forums for specific advice.
I agree entirely and wholeheartedly. The Riviera is little more than an ill-fated mess, a total abomination of audio engineering, and a waste of perfectly good silicon. It is sonic processing at its absolute worst.
And that's why I use one.
Seriously, though. This thing sounds sweet paired with a small vacuum tube power amp. It easily reproduces sound with fidelity that is on par with cards twice its price. It records with equal results.
Don't knock it 'til ya try it.