I just want to put in a plug for Appro dual opteron servers, in case anyone is still looking for a solid dual-opteron solution. Anandtech did a glowing review of Appro servers a while back, and I've been using them since 2000. My last server ran for 5 years straight without even a blower going out

They're currently offering a 1U and 3U version. Not the cheapest servers out there, but very solid.
http://www.appro.com/product/opteron_main2.asp