I would also agree. I think going any higher than a 7770 would bottle neck that CPU. Personally I would update your CPU and then get a new GPU at a later time if you can't get both at once.
I am not really up on intel anymore but from what I could see that CPU is a socket 1155 and if true you should be able to find much better CPU's that would work with your motherboard. Then I would get atleast a 6950 or better depending on your budget. But it would help to know what make/model motherboard you are using first.