I have the x530s and got an X-FI xtrememusic after my onboard sound fried somehow...there is a bit of a difference in sound quality particularily in games IMO and it picks up my mic better I think, but other than that I don't think a sound card is worth over $100 unless you're doing more recording/mixing and crap rather than just playback
It's a decent card, I just don't think it's worth the pricetag and the whole "CPU Load" thing is complete BS considering you can't honestly think a CPU isn't powerful enough to process some basic wav or MP3 playback...I guess I'm just picky and wanted something that had fairly decent backing from most sources