Big B, thanks for giving consideration to my post.
I did a small calculation based on this link:
http://forum.ncix.com/forums/index....nt=15&subpage=1
7800 GS = 51 watt
watt = volts x ampere, then..
51 watt / 12 volts = 4.25 ampere
I am not sure if this calculation is accurate enough, so...