i have a radeon hd 5770 and quite honestly, its an awesome card for gaming, running SC2 on ultra with no lag which is good enough.
however, if you wanna look at benchmarks,
Tom's Hardware's got it.
according to that link, clearly a GT460 is better by around 10fps... but im still sticking with my R5770 cause its damn cheap.
edit: just realized that the other card on the website is a GTX not a GT, but oh well...