Let me put it this way, I would only 'consider' the GTX460 1GB if I can overclock if I can overclock the Athlon II X245 from 2.9GHz to 3.8GHz...and even then, I'd probably just grab a GTX460 768MB.
If I'm not overclocking the CPU and leaving it at stock speed, I would get a 5770, as using any faster graphic card is not going to be much faster than the 5770 with the CPU bottlenecking...I 'might consider' the GTX460 768MB though.
Besides, for 720p the 5770 is more than capable. If for 1080p/1200p, then I would probably recommend the GTX460 768MB/1GB...but not until that CPU is overclocked to higher clock speed.
Right now whats on my mind is. Get a 5770, after a year get a new monitor, get a better cpu and then buy the gtx 460/