Dont forget a new psu too, whilst he Cosair CX400 is a good choice as recomended earlier, Id be tempted to try n get something better so you can carry it over to your next build rather than have to buy another new one next year, eg
Palit GeForce GTX 460 768MB GDDR5 PCI-Express Graphics Card £112.79 (£95.99)
Corsair TX 650W ATX SLi Compliant Power Supply (CMPSU-650TXUK) £73.99 (£62.97)
Sub Total : £158.96
Shipping cost assumes delivery to UK Mainland with:
DPD Next Day Parcel
(This can be changed during checkout) Shipping : £9.50
VAT is being charged at 17.50% VAT : £29.48
Total : £197.94
Both these could then be reused when you rebuild main part of system, whenever you have the cash