I looked at OWC store first thing.. The price for 16Gb kit for the 3,1 version Mac Pro is a bit high (about $600), so I am wondering if somebody selling used memory.. If I will not find any, I will go to the OWC for an upgrade..
Have you tried looking at OWC? I got 16Gb for my MP 3,1 a few years back and the prices were pretty good. Would love another 16Gb to feed it's hungry belly.