Chillblast are good but for me alienware are the best,
I recently bought a pc from them for gaming and was well impressed with them.
It took next to no time to reach me and looks amazing too.
Try this one.
Once you have selected all the bits and peices for it, it should come to around £2000.
Only problem i had with my pc from them was that the pc was too powerfull for some of my games :)