My RANT (MOAN):
This is the argument i have with alot of freinds, AMD are nowhere near as advanced as intel, ok AMD are cheaper, and most of the time do there job just fine. Intel will always be the best, i think intel have future processors already designed but are waiting for the world to catch up.
When buying the 8-core i hope you wasn't expecting a miracle, the thing with the cores, is most applications can only use 4 of them, with mainly Rendering applications that can use all 8. You should have spend you money on a powerful 4-core, especially for a server.
This would mean instead of having 8x3.2GHz where only 4 are usable.
You would of had 4 x 3.8GHz more power with more use + Turbo on Intel means you can get 4.2GHz out of them easy.
Always buy intel, and sorry if this isnt much help!