I recently built my own machine and it's been working great, save for the sound quality. In fact, low sound quality was one of the first things I noticed - when windows 7 started up for the first time, a pop interrupted its startup jingle. Ever since, I've been getting intermittent pops and crackling when playing music (doesn't happen so much with games).
For a while, I'd been running the speakers on my ASUS monitor. I thought it could be a problem with them, so I switched to headphones - still there was crackling. I switched speakers again, this time to an old set of Labtec speakers in my old tech box - still, there were popping noises.
Hmmm,, your link leads to a page that contains a lot of open box items and yours is not there, now then ,,, you did not buy an open box item ??, 'cause if you did , it is just that when one buys an open bx item online it is not like going to the local brick and mortar which may still offer some warranty...[To say nothing of shipping charges]..............
Having said that, the only other suggestion that comes to mind,, is to try another psu even if you have to disconnect a few items for a lower wattage, or try it in a buddys computer, after all it is just a matter of drivers nothing to it... ..