PSU..stock 300 watt i am going to upgrade im looking at this PSU, it will fit in my case and has the connectors i need.
CORSAIR Enthusiast Series CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC
Compatible with Core i7 Power Supply......http://www.newegg.com/Product/Product.aspx?Item=N82E168...
GPU..radeon HD5450 DVI running at 1440x900 resolution
It's not overkill. By the time you crank up the graphics settings, especially Anti-Aliasing (4xAA) you can easily max out the card.
My advice would be the GTX560Ti Asus or MSI card. The difference in price between this and the other cards is very little when compared to the total spent on all the other hardware and games, AND the graphics is the bottleneck so every $50 makes a noticeable difference.
Beyond the GTX560Ti it's a waste of money for you though.
Never get a GTX4xx series. They run far too noisy and hot.
The NVidia cards also have PhysX (for physics) which the AMD cards do not. That takes away from your frame rates which is also why I recommend the GTX560Ti card. you'll need it for max (or close to max) settings on most modern games.
my old gts 250 could max out new gams at 1440x900 no problem (even crysis 2, crysis 1 on "high", bfbc2) so yeah a 550 ti should be good for that resolution. but if you're going to upgrade to 1920x1080 you should get a more powerful card