I personally use a Creative ZxR, great sound card and 1/4 jacks! People say the software doesn't work but it works perfectly for me. My board is a Asus VI Formula which already has super good onboard compared to most but doesn't compare to the ZxR.
If that's too much then I'd go with a Zx. I like Asus a lot but when it comes to the sound I feel their cards are better for gaming than music, but they probably really aren't, it's just my opinion.