Right forget about what he said about Quad processors and the 4800+, you should get yourself a Intel Core 2 Duo E6300 for 2 reasons, if you overclock this to roughly about 3GHZ it can wipe the floor with the top of the range AMD FX 62, if you wish to leave it standard then its the equivelant to the AMD 4200/4600+, it beats the 4600+ in most benchmarks but beats the 4200+ in all benchmarks, so its deffo better to get that than a 4200/4600. As for the water cooling there is no need to get that unless your are going to mega overclock and there isnt a motherboard that lets you max the overclock performance of the Intel core duo at the moment, all you would need is a upgrade CPU heatsink that would cost you about £20/£30, it can be overclocked with the stock cooler as far as 2.7/2.8GHZ i think but its safer to upgrade the heatsink. Here are a few motherboards that are good for overclocking or just running you CPU off, Gigabyte GA_965P_DS3 (Socket 775) PCI-Express DDR2 Motherboard or Gigabyte GA_965P_DQ6 (Socket 775) PCI-Express DDR2 Motherboard, the DQ6 is the better model, but both do the same job, i would recommend one of these, if you dont want to overclock straight away it always leaves you the option for overclocking, as for RAM, Corsair 1GB DDR2 XMS2-6400C4 TwinX (2x512MB) something along those lines, good quality high performance ram, depending on the GFX you want, most games demand CrossFire or SLI, personally a single GFX card would suit me,the Sapphire ATI Radeon X1950 XT 256MB GDDR3 takes my fancy, looks to be a very nice GFX card for only £187, it really up to you tho. . I am aslo building a Intel core duo setup just now so ive been doing my research aswell, hope this can help ya make up your mind m8.
/Sic
Also im sure that the FX chips that are single core only go up to the FX 57, anythin above are Dual core, not worth buying these days i think tho. Overclocked E6300 ftw :P.