If you don't want to spend alot of money and you also don't want to use onboard then look for a Audigy 2 ZS, should be pretty cheap now.
I have one, it preforms well.
If you want to spend a good amount look for the Blue gears Mystique. (I don't think neweeg has it anymore)
The High End would probably be Creatives card with all the extras.
(External Box, Remote, I think 250+ ish)