Looking to make a gamins system for - 700 pounds



Now I didn't really know where to put this as I won't be building it myself. I want to use a pcspecialist-type site where you can select all your components. So first off, any recommendations for a good site? I did make a pretty good build at ecollegepc.com but they only deliver within the US (I'm in UK). So the best I have found since is http://www.cougar-extreme.co.uk/ - seems like they have only good feedback. This is what I have, any thoughts?:

Intel Core 2 Duo E8400 3.00 GHz
4Gb Corsair Memory DDR2 800 (2 x 2gb)
300GB SATA Hard Drive
Asus TA-D31 case
Colors 550Watt Silent Upgrade
512MB 9800GTX+ Nvidia DDR3 DVI
Asus P5Q motherboard - 1600FSB-DDR2 1200x4
DVD+/- RW - 18X Samsung Lightscribe
64 BIT Windows Vista Home Premiem

Now that comes to 674, but I'm worried about the case and psu, primarily......


An alternative build using amd:

AMD Phenom II 720
Case - Cooler Master Elite RC335 Black
600w Cooler Master Extreme Power Duo
Asus M3N72-D - nForce 750a SLI Chipset
4gb Corsair XMS2 DDR2 800mhz CL5.0
320gb SATA2 Hard Drive
16x DVD Drive
512mb Nvidia GeForce 9800GTX+
Windows Vista Home Basic (64 bit)

For 650, which would give me some leeway....