This is my problem, I usually always go for the model under the premium card, but this time around your screwed if you do that because your really not gaining much in terms of performance upgrading from a 670 to a 770, so your kinda forced to upgrade to a 780 if your in need of a performance jump which is an extra £200-£250, the 780 imo is what the 770 should be.
I'm not happy with nivida this time around what with the titan con job, we all knew it was a scam to bulk up the price of the 780 on release, and at only 27% performance gains over the 680, ridiculous.
I wanted my decent 'price to performance' upgrade (which would have been the 770) but nivida have moved the goal posts.