its ok, everyone learns from experience, this video card recommends that you use 450 watt power supply.
-Willpower
450w ok... But what kind of amperage do i need on the 12v rail? Like I said in my pp i have only 12amps with the psu i have now... I saw on these forums someone saying you would need 28-30 amps. Seems a bit much, am I wrong?
Your not wrong, the X1900GT is a power hog
12amps is pretty low, it would be a good idea to get a new PSU as inadequate power could lead to overheating or system failure
PSU 101 sticky - this should help you pick out a decent one.
Basically you need a brand name PSU like Antec or FSP that meets the power requirements (minimum of 450W, +12V @ 28A)