Dell power supplies from delta are quite efficient, I believe any of these cards should work for you. I suggest going with the 5750 if you can find it within budget, I ended up getting the 5770 cause it was only 10 more.
ok thanks then the question is which one of these is the the best preformance wise? The main reason i want this upgrade is to get a gaming graphics improvement, so which one should i buy? also, are there any other cards (less than £100) that i should be considering that would work on my system for gaming?
A 5750 usually out performs a 4850, I think the 5750 is the card for you. Mostly because it can game and it is exceptionally power efficient so it shouldn't tax your PSU too much. I don't really know how the pricing works out in countries outside of the USA. I was able to get my 5770 off ebay for around $120. I am totally comfortable buying from ebay though. But as for going retail and needing a card that is Power efficient, I think the 5750 is the best fit, much better than either the 4770 and the 5670.
If you ever change your setup(CF mobo + new PSU), you would be able to crossfire and get some impressive results. both CF 5750 and 5770 results very tempting to me.
hmm thanks for the reply. if you were wondering i can get a 5750 for £80 new in the UK, but are you certain it is better than a 4770? (which i can get for £65)
I have never used a 4770 and directly compared it with a 5750. I was basing my answer off what I have read. The 5750 is on par the 4850, some games may give a better FPS to the 4770, but overall the 5750 beats the 4770. This link compares the CF 5770, CF 5750, 5770, 5750, and 4770