You can use a power supply wattage test to help you choose.
This one by Asus suggests 950 watts as a minimum required rating.
This one by Thermaltake suggests 600 watts minimum.
Personally I would go for 1000 watts, as it allows enough headroom for future upgrading, and because the closer you get to a PSU's maximum rating, the less efficiency it is and produces more heat and fan noise. I cannot find your PSU anywhere, but any Cosair PSU from the HX, TX or AX series get's my thumbs up, as their products and service/customer support has been flawless in my experience for over 5 PSU's now.
PS. I find that putting SSD's in raid is useless, as you lose TRIM control and don't get much performance increase.
Any reliable brand (Antec, Corsair, Seasonic, and Silverstone are all reliable brands) at 750 watts should be fine. Then its just a matter of reading the "bonus" features and choosing to taste. A lot of builders like "modular" PSU, which lets you choose which cords you want to add and leaves to a cleaner case, but they cost more and lower your options. Others really like PSUs with quiet fans, or like PSUs with a great deal of energy efficiency. Anything with the 80+ certification has to pass tests that ensure at least 80% of the electricity taken from the wall goes to powering the computer versus being wasted as heat.
I'm going to build a gaming pc and I'm unsure what power supply to get I'm looking at a Corsair 750w pro, but I'm not 100% help is appreciated.
-Intel core i7 3370k.
-Corsair H100i water cooler.
-2 (gtx 660 in sli)
-2 (4gb corsair vengence 1600Mhz memory)
-4 (OCZ agility 3 60gb in RAID 0)
Asus p8z77-v deluxe motherboard.
- Thermaltake Level 10 gt snow edition.
Hi - realhardtech(their expertise) suggests a quality 620w PSU for a sys running
two gtx 660's in SLI. So, a quality PSU in the 620w range (min 36a on +12v rail) is
sufficient. You might want to consider a 650w unit from a quality brands as there
is usually deals on the 650's. Quality brands:
You don't need 1000w or anything close to that. No harm in getting more than 650w,
except to your wallet.
Seasonic, XFX, PC Power & Cooling, Rosewill Capstone/Fortress/Tachion series,
Silverstone, most Antecs, most Corsairs, most Enermax, & a few others.
An excellent deal on a modular platinum rated unit:
For a system using two GeForce GTX 660 (non-Ti) graphics cards in 2-way SLI mode NVIDIA specifies a minimum of a 600 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 36 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors. If you have the MSI GeForce GTX 660 HAWK 2 GB, it requires two 6-pin PCI Express supplementary power connectors for each graphics card, so you'll need a total of at least four 6-pin PCI Express supplementary power connectors on the power supply unit.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the critical factor.
Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.