Well maybe move up to a 7750? Not sure if it's worth the spend if you're only moving up a notch or two. Helps to set an absolute limit. Thing is, below a certain point (typically around £100) you'll find as you move down models, that performance is dropping off faster than price. Above a certain point (usually around £200) you'll find price increasing faster than performance. With that in mind, the best purchases tend to be between £100 and £200. Below £100, you really will find you're getting significant advances in performance as you step up each £10-20. This might be helpful:http://www.tomshardware.co.uk/gaming-graphics-card-review,review-32571.html
The second and last pages especially.