Help with upgrade

Ok so I'm gonna have $300 to spend the 20th and am planning on upgrading my graphics/cpu with it. My main interest for the system is mostly to be able to play GW2 a bit smoother, fps shoots down when in cities/WvW/lot of people in general. Figured the fps issue was due to the cpu, but im not sure how to balance the money to get the best out of both.

Resolution: 1680x1050

Currently:
MOBO: 870-G45 (MS-7599) 2.0
GPU: ATI Radeon HD 5700 Series
CPU: Athlon II x3 450 (Rana)

Looking at:
GPU:Radeon HD 7770 GHz
CPU:AMD Phenom II X4 965 Black Edition

Now while I don't know the latest news, i figured it would be best to get some advice on possible better selections for my price range (i.e. more expensive cpu / cheaper gpu , more expensive gpu / cheaper cpu).