I have played a bit on both the 280 and the GX2 with similar rigs and I'd definately say the 280. The GX2 is essentially two 8800GT, with a few extra pixel shaders and pipelines, in a single card. The 280 is a whole new architecture, kinda like the next generation of processors and stuff, so I'd suggest if you want something for the future, that's the best option. Most of the reviews and tests I have seen suggest this card is significantly better than the GX2, but whether it's worth 100 pounds more, I'm not sure.