Actually, pez-king, your specs are very similar to what I'm currently building.
You'll need a 3500+ or 3800+, since currently those are the only ones for 939 pin (unless of course you are buying opterons). The 3500 is probably the better choice, because the 3800+ is about $300 more. Seriously, dude, this upgrade is painfully expensive, so I'm hoping this upgrade will last me for a while.
it is nforce 3 250.
As for the RAM, I'm getting just 512MB (2x256) of Crucial's Ballistix memory. Sure it is only PC 3200 RAM, but the latency kicks arse.
Other than that, your setup is going to match mine almost exactly. I'll let you know how it turns out. I don't think the power consumption is going to be too bad. I mean, heck, shuttle built these things to be able to handle the X800. Since I'm not using anything in the PCI slot, I should be good power-wise. But, just to be safe, I'll run the math again.
Until then, peace out.