470 runs around 26@120
480 runs around 29@135
Theoretically its possible to run 470 at 28, but it requires hardcore mem OC and not many cards can handle it 24/7.
my powercolor red dragon 470 4 GB single fan does a hair over 29 mhz on eth with the 1750 strap mod. 1200/2100 -75mv. 24/7 stable. no idea of the power draw at the wall though but gpuz says 85 watts for the chip only. it is undervolted and underclocked core wise.
need samsung memory is the main thing for the 470 29+ club.