Recommending 3GB on the graphics card is still quite controversial - especially if you're only running at 1080P. I'm not saying that it's necessarily a bad recommendation, but I am pretty sure that saying you'll need to replace the GPU in 12 months if you have less than 3GB is bollocks!|
AMD have been two or three percent ahead of nvidia in price/performance for a few years now, but the advantages of a nvidia card still outweigh that tenner, IMO: decent driver support, actual Linux support (which used to be a niche selling point, but with SteamOS now announced it's safe to say that 'if you get an AMD card you'll be changing it in 12 months' ), Gsync, and fewer micro-stuttering issues (which may link back to the AMD driver issues). Also remember that the "280X" is a rebadged 7970, which is years old and heavily-squeezed, while driver updates will continue to improve the GTX 760/770 performance.
If you're not in a hurry and you can stomach the vultures at HUKD, you might want to keep tabs on their computing deals section, and pick up bargain components one by one over about a month. GTX 770s have dropped as low as £277, but that doesn't put them in Bargain Town yet - at least, not until October 28th, when the nvidia games bundle will change from Batman: Arkham Origins to Assassin's Creed IV, Batman: Arkham Origins and Splinter Cell: Blacklist.
Maybe "overkill" is too strong a word, but a GTX 770 at 1080P is certainly a heck of a lot of future-proofing! You could also consider getting a £150ish card and replacing it every year while selling the old one for £140ish. Less initial cash outlay and less depreciation on your investment while keeping at the cutting edge of feature support.