According to wikipedia:
AP has sold over 250,000 copies.
That number is actually really outdated. The total for Absolute Power was given as 313,000 in that Billboard article a few years back. Anghellic had 278,000 with Everready at 180,000. Though those numbers are from July 2009, so they're likely a touch higher now.
However you have to consider that they spent four years or so pushing Absolute Power too. It dropped in 2002, and hell... they were still doing "Absolute Power Tours" in 2004. I think that helps account for that album being the highest selling album. Anghellic was cut short in it's initial release, and then was re-released in the wake of AP. Then once Everready hit, they haven't really spent any time pushing an album as we've gotten a new album each year since. Or two in some cases.