Simply GTX 460 is better than HD 5770.
GTX 460 is a beast.Buddy your CPU is a limiting factor for GTX 460.
If u have budget than simply go for GTX 460 (Superclocked Version).
But a slight OC can solve your problem.
GTX 460 will be bottlenecked by your CPU to some extent.
With GTX 460 your combination will be very good.
Best Of Luck.
performance wise it is worth the extra cash if you really has it. not to mention 460 is quite a monster in overcloking. so even if you get the reference model you still can fork out the performance out of it. cpu wise i think your cpu will be a bottleneck for the card so you might want to OC your cpu a bit. just be sure you have the right PSU for your system and you'll be good to go
thanks for your responses I have just purchased the Palit GTX 460 and as to OC'ing the CPU I have no clue on how to go about doing so I tried installing the Intel Desktop tool and it says "wrong platform" something like that so apart from using desktop software I have no idea how to Overclock a CPU..