the 6600, the X600 is just a pci-e 9600, a 6600Gt would be best, but on a budget a 6600 will do once overclocked, you should get near 6600Gt speeds anyway.
You're looking at a lot of excess p&p cots going to so many places, it may be worth pricnig the lot up and each one on it's own and seeing if it works out cheaper overall from one of them.
I recomend this drive if it isn't what you plan on already
http://www.microdirect.co.uk/Product...87&GroupID=601
Is that a dual channel kit for the ram? if it's not it's really worth going for one, this one's £41 and it's worth going for as performance is much better than a single dimm
http://www.overclockers.co.uk/acatal..._ValueRAM.html