Is this psu good enough?

I was wondering if 700W would be enough to run my setup below? psu calculators seem to suggest that it will be, but I don't know how accurate these are...

My build:

i5 2500k overclocked to a maximum of 4.5GHz (don't want to risk pushing it further)
2 x HD6950 or 2 x 560ti's (planning on overclocking either setup)
1 HDD
4 x 4GB DDR3 RAM


This is the psu I'm planning on using:

Coolermaster Silent Pro 700W Modular PSU - Single 12V Rail with 50A

I would up the wattage a little
I would pick something in the 800 watt range
something like this one
http://www.newegg.com/Product/Prod [...] 6817371024
the four companies you will see everybody recommend here is
Antec,Seasonic,XFX and Corsair
try looking those brands in the 8xx wattage area
just in case you add more powerfull GPUs later or more HDs you would have more room for expansion

Get a power supply that actually has at least four PCI Express supplementary power connectors required for two Radeon HD 6950 in 2-way CrossFire mode or two GeForce GTX 560 Ti in 2-way SLI mode.

The Cooler Master Silent Pro M700 (RS-700-AMBA-D3) has only two (6+2)-pin PCI Express supplementary power connectors.

Since you're planning on overclocking get a power supply with more than 50 Amps on the +12V rail(s).

how much does it matter that the psu is not modular?

I think i'll spend a bit more to try and reduce cable clutter... these are the best priced modular psu's in the uk that i could find... could you help me choose?:

http://www.ebuyer.com/176413-coole [...] m=products

and

http://www.scan.co.uk/products/800 [...] e+shopping

oh ok! I must admit that i saw the cables and assumed that it was modular... didn't look close enough...!

How reliable are xfx as psu's? i've heard that antec, corsair and coolermaster were the ones to go for?

XFX is as good as any of the high-quality manufacturers. My short list at highish wattages (by quality, not price; some of these are expensive):
NZXT, Thortech, Corsair, Antec, OCZ, XFX, Silverstone
NZXT's HALE90 and Thortech's Thunderbolt are some of the best PSUs out there, but all of these are very good.

You honestly don't need the 850W. http://www.tweaktown.com/reviews/3 [...] dex17.html

PSUs generally hit peak efficiency somewhere around 60%, so the 850W will be more efficient in gaming. You're right.

The power supply only provides as much power as needed by the system. If the system is only demanding 300 Watts at the moment then that is what the power supply will provide. At the wall outlet the power consumption will be more than 300 Watts because of the conversion efficiency losses (e.g. 375 Watts for a PSU with 80% efficiency).

The power supply is not outputting a continuous 850 Watts all of the time.

Higher efficiency power supplies will use less electricity and generate less heat and therefore run cooler.