There isn't anything wrong with the PSU you've listed. It's just that a lot of people hear of Alienware's shit using 1000W PSU's and thinking that must be some kind of minimum requirement for a gaming PC. It's not. Alienware, along with a lot of 'gaming PC' manufacturers throw in a lot of shit you'll never, ever need.

However, the reason you get a good PSU is to avoid power shortages and fluctuations damaging your PC's components. The more strain there is on your system the less time it lasts. Yours is fine. Overkill, really.
Corsair are good VFM and have decent extended warranties. I'd go with that if you're going to switch.

Okay, thanks for clearing that up.
Well, I've decided I'm tired of my mother controlling me and I am buying the desktop regardless of what she will do when she finds out. Wish me luck. =)

EDIT: BUMP.