Re: Which card to buy?
I prefer single card solutions myself, and I'd be leaning towards either the 260, or the 285. The 1Gb memory on the 285 means plenty of buffer for the higher rez. To give you an idea, i have a 280, and my flatmate bought a 295. I get no slowdown in GTA4 with high textures, he gets slowdown every 2 - 3 secs because he has less memory buffer.
Yes, the 4870x2 might only be £10 more, but the 285 performs nearly as good, and it's only 1 card.
The Q9550 is a good choice, very nice CPU. Overclocks nicely.