August 17th, 2013 
CryptoBadger Amazon currently has an excellent deal on a Cooler Master 1000 watt gold-certified fully modular power supply. It’s $125 after a $30 mail-in rebate, which makes it about $75 cheaper than its normal price (new units on eBay typically sell for nearly $200). This PSU is reportedly a re-badged Seasonic and should have no problem providing efficient power to a rig with four undervolted 7950 GPUs (or three full-voltage cards).
Update: Looks like the deal has ended. The rebate is still available, but Amazon has raised the price back to its normal level. Hopefully some of you were able to snag one!
Update: The deal is still valid, although it looks like it’s been pretty popular, with shipping estimates in the 1-2 month range.
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The sale must have just ended I only see it for $200
Do you know if I can run 3 undervolted MSI cards of this PSU?
Corsair Enthusiast Series TX 850 Watt ATX/EPS Modular 80 PLUS Bronze (TX850M)
http://www.amazon.com/gp/product/B005E98EI2/ref=oh_details_o01_s00_i02?ie=UTF8&psc=1
Yup, it looks like Amazon pulled the deal – that was quick!
It looks like I answered your question over here just as you were typing this one. Short version: yes, that PSU will be fine for 3 undervolted 7950 GPUs. =)
The Amazon link you gave is for a specific merchant who is selling them for $209 – Amazon themselves are still selling it for $155:
http://www.amazon.com/Cooler-Master-V1000-Modular-Certification/dp/B00CGY4ETG/ref=sr_1_1?m=ATVPDKIKX0DER&s=electronics&ie=UTF8&qid=1376754042&sr=1-1&keywords=Cooler+Master+V1000+-+1000W&tag=cptbr-20
Ah, thanks for the catch – I’ve updated the link.