Help with a full upgrade?

Philis

Honorable
Dec 2, 2013
4
0
10,510
Hi there, I was wondering if you could help me. I don't know much about computers, and am a bit older, but I like games, I bought quite a high spec pc (for me) in 2009 these are the specs:
Phenom II X4 Processor 3,200 Mhz
4GB Ram
Radeon HD 5750 with 1024Mb of Ram (core clock 850)
I have now upgraded from Vista to Windows 8.1 on a normal Hard Drive of 1Tb
I have a budget of about £250 or $400.

The system does everything I want in terms of Office Applications, but I wonder if I want to play Crysis 3 or Call of Duty Ghosts if I would be better upgrading the graphics card, or if then the CPU or the memory would be too slow to make use of the new graphics power?
Would you recommend a CPU and Motherboard upgrade, or just a Graphics card upgrade and if so, which Graphics card would show a significant improvement over what I have now? I am a fan of AMD products and try to use them when I can. I only use one monitor at resolution 1366 by 768
I hope this question makes sense, many thanks, Philis