like landshark said, if you just use big slow fans (or just even small SLOW fans) like vantec stealths or other fans and 7V mod them it will be silent. Your HDD spinning and seeking will make more noise than the fans. (yeah we can always go crazy and use solid state flash HDD's but lets get real)
In the end, cool design, nice concept, but just not practicle. This is for people who don't have the time to construct thier own setup and want something to look nice in thier living room. Definetly not for me though, I'd rather build my own, save the cash, and be upgradeable!