I'm thinking neither of the PSUs in the "often bought with" section will work well with the Asus dual Opteron mobo as they have the EPS-12V (dual Xeon) ATX connector that might not be the same.. I'm checking now - yup, the pinout looks OK. So the Sparkle FSP550-60PLG should work great with that and it can be had for around $85. per Froogle. Probably significantly less than those others.
. And I have a Delta 465W unit here that was made for HP workstations (they still sell replacements for $150.) and it has 39A total on the +12V (22 for the CPUs and 17 for the rest) but I'd have to rearrange the ATX connector to suit your purposes. It's a shelf-sitter that's never been used and it's a bit higher and deeper than standard ATX size (at 6Wx4Hx6+deep) plus it has a 92mm Delta fan inside. It weighs all of 6 pounds! Most good cases could take it w/o much modding (these Skyhawk cases that the egg was blowing out fit it nicely. PM me if you're interested.
.bh.