there is no insurance that undervolting will yield same results (I tried undervolting my 955BE C2 and succeeded).I wouldn't recommend buying a CPU and hoping it could be undervolted.Just like overclocking, each CPU is different
@Timop
GTX 260 is in the same league as the 4870 & the 4870 is a bit faster than the5770 (probably due to the 128-bit memory inteface)so, its only natural that the GTX 260 is better than the 5770.