It's cheaper than the i7 980 and the SB chips overclock so well, with a good cooler 5.0 Ghz is easily achievable. It's newer tech as said above and the new Z68 boards and will have a longer lifespan.
With £2k for just the tower I would go for something like this:
OcUK GeForce GTX 580 3072MB GDDR5 PCI-Express Graphics Card **Supplied with FREE Batman: Arkham City PC game** £399.98
(£333.32) £799.96
(£666.64)
Lian Li PC-P80N Full Tower Case - Black £249.98
(£208.32) £249.98
(£208.32)
Intel Core i7-2600K 3.40GHz (Sandybridge) Socket LGA1155 Processor - Retail £239.99
(£199.99) £239.99
(£199.99)
Asrock Z68 Extreme4 Gen3 Intel Z68 (Socket 1155) DDR3 Motherboard £159.98
(£133.32) £159.98
(£133.32)
OCZ ZX Series 1000W '80 Plus Gold' Modular Power Supply £143.99
(£119.99) £143.99
(£119.99)
Crucial RealSSD M4 128GB 2.5" SATA 6Gb/s Solid State Hard Drive £139.99
(£116.66) £139.99
(£116.66)
Samsung SpinPoint F4 EcoGreen 2TB SATA-II 32MB Cache - OEM (HD204UI) £127.99
(£106.66) £127.99
(£106.66)
Thermalright Silver Arrow CPU Cooler (Socket LGA1366/LGA1155/LGA1156/LGA775/AM2/AM3) £54.98
(£45.82) £54.98
(£45.82)
Corsair XMS3 8GB (2x4GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (CMX8GX3M2A1600C9) £42.98
(£35.82) £85.96
(£71.64)
Samsung SH-S222AL/BEBE 22x DVD±RW SATA Lightscribe ReWriter (Black) - OEM £18.98
(£15.82) £18.98
(£15.82)
This comes to £2040 inc VAT and shipping.
That would be a BEAST and the best solution for all your needs within budget imo. The 3GB 580s will be the best for ur resolution when you get the other monitor. Price Vs Performance the 6950s are better so if you want to save around £360 now and get the third monitor now, do that.
EDIT: Although to be safe I'd prolly spend less on the case and get this PSU just to be sure:
http://www.overclockers.co.uk/showproduct.php?prodid=CA-054-OC