I guess the only question is, Would you buy a dual socket system that wasn't QFX and why.
At work for my datacenter, no.
However, the REAL question is, Would you buy a quad-core system that wasn't Core 2 Quad?
Well, I think that answer should be pretty obvious. Of course I would. FX70 is up to $900 less and I believe will clock to 3.0GHz (not that I will).
FX-70 MSRP = 599 per pair
This recovers the extra $150 to $200 caused by a more expensive motherboard.
This also recovers the extra $50 to $100 for a more expensive power supply.
So a FX-70 would cost $100-200 less than a Core 2 Quad system when you factor the motherboard and power supply issues in. However, the performance hit you take from going 3.0 to 2.6 is tremendous (13%).
So even the cheaper FX-70 is still going to have price\performance issues when battling the Core 2 Quad. You can't just factor in processor prices when the "platformance" of Quad FX requires you to have a very expensive motherboard and a beefier more expensive powersupply.
But what you have to remember is that because I have 4400+, I don't lose anything by NOT buying C2Q vs QFX. Also, I am not comparing against C2Q, so I dont' care if it's faster.
The Inq has shown that most PSU reqs are grossly overstated as they got 3 8800GTS running in one mobo with C2Q and a 620W PSU at load with 3dMark.
Anand got idle power of FX74 with 8800GTX and Raptor RAID to 213W. You are all exaggerating because I have yet to see anyone complain about dual Opteron.