Hey Salacon, I think you know who I am, right?
Some food for thought ...
If your upgrading this summer, no sense in buying old technology (Socket 939). But at the same time, Socket AM2 isn't quite worth buying yet, because then you'll have to buy DDR2 memory which doesn't have low enough latencies yet IMO (for AMD).
So I'd really reccomend looking into Conroe for the CPU. That also means that you'll need either a 965 or 946 chipset, Socket T (LGA775) motherboard. And some DDR2 memory, try to go with 2x1Gb with low, low latencies. Also, eVGA is definitely the best Nvidia "company", and their KO 7900GT is easily the best 7900GT out there. That isn't going to change anytime soon, so that's your video card.
And if you do decide to go with your setup, stick with the Opteron 170, or if that's too expensive then a Opteron 165. And 2x1Gb G.Skill or OCZ PC4000 memory, the eVGA 7900GT KO and the DFI Nforce 4 Ultra-D.
No sense buying an SLI motherboard, because first off SLI just sucks for the most part, and you won't even be using SLI!