In my recent build(ordered last night) I was in the same boat as you but in the end I went with the 95w 945 deneb since a lose of 200 Mhz and some easier accessed OC features was a decent trade for lower power consumption and (i hope) lower heat and therefore higher OC'ing potential. (plus it was 10$ cheaper) (All the prices I list are from newegg aside from the video card which is BB, the pricing is all dependent on current deals and sales that end around the 16th-19th of Nov.)
ASUS M4A79XTD EVO AM3 AMD 790X ATX Motherboard Combo deal with most of the Phenom II X4's ~ 30 $ off + it's on sale from 120 to 105 w/ free shipping
Antec 650w Earthwatts - Bought it with a Antec 300 combo deal for 109 w/ free shipping
AData 2x2GB DDR3 1600(PC3 12800) ~89.99 w/ free shipping when I bought it no combo deals for it.
VisionTek ATI Radeon HD 4870 1 GB version. (BestBuy is having a good deal on these, got it for 149.99 online)
With all the deals /etc my grand total (with shipping +7% NJ sales tax) came to 648~$
If you are considering SLI/Xfire go with a 700+ watt psu from Antec/Corsair/OZC. They range from 100~ish to around 150$, alot of the Antec New Truepower series have nice combo deals going on at newegg. You could probably eek by on a 650w PSU but personally I like not coming within 100+ watts of the PSU's max continuously. Also if you are considering SLI/Xfire you may want to check out the Dual GPU cards ie nvidia gtx 295, radeon 4850/4870/4770 x2. With the launch of ATI's new 5000 series these are coming down in price aside from the 295 which is at it's steady 500+(if you can find them). Also you may wish to check out the 5870 & 5850's their power consumption compared to SLI/Xfire and dual gpu cards is considerably smaller which may allow you to save some money on a PSU. Compared to the dual gpu cards they lose a bit in performance but with DX11 and Eyefinity( spreads the image across 3 screens) and about the same pricing (lower in the 5850's case ~ 260-300$, 5870 360~400$) it may turn out to be a better deal for you. The only problem with the 5870 & 5850 is that they are sold out in most places... and go like hotcakes when a deal gets them in.
Yes, give us a budget. What was suggested two posts higher is great, other than the case (which is more expensive than needed) and the graphics card (which is weaker than I'd like). Perhaps get a slightly cheaper case and throw a few more bucks against it and you'll get a latest generation graphics card (or at least a 4890). Much better performance given its relatively price premium.