The original HX650 is not that good of a buy in this day and age as there are newer, better, cheaper units available.
Besides you don't need as much as 650W for a build with a GTX 550 Ti and no SLI or overclocking, now or in the future.
Seagate's HDDs are know for their unreliability, so you might want buy WD Caviar Blue/Black or Samsung SpingPoint F3 HDD instead. And the case you've picked is mainly aimed at the extremely low budget builds, which this obviously isn't. So I'd recommend you to invest a bit more on the case, as a quality case will last you many more years. Check out the Fractal Design, BitFenix, and Corsair's cases as well as the higher end CM cases.
In addition, the PSU is overpowered, as that rig will hardly hit 200W power consumption under stress... A quality 400-500W PSU will be more than enough, leaving you room for a possible upgrade in the future. Also, I'd suggest you to grab a dual memory kit (2x8GB).