AGP2x was 3.3v, that was the original spec. AGP4x was specified as 1.5v, but some early AGP4x cards were made for 3.3v to save $0.10 in manufacturing cost, and can't be used on current boards. All those are off the market now unless you buy them used.
<font color=blue>Watts mean squat if you don't have quality!</font color=blue>