I need urgent advice om my system power and hardware compatibility.

[Bobby the second]

I'm buying a new system and so far it looks as follows: A cooler master midtower case the RC-p100k-KWN2 With windowed side-panel, 4x coolermaster extraflow fans, the v6 CPU cooler, core i5 2500k, a GIGABYTE GA-Z68X-UD3P-B3 motherboard, 2x4gb patriot viper extreme division 2 memory, a TB of hdd space and two gigabye overclocked edition radeon 6870's. They have three fans each so temperature is not one of my concerns. I am however worried about my power requirements. My options are a 750w gx from coolermaster or their silent pro gold 800w. Please note that I wish to overclock and my main concern is whether my power will remain stable and if my system can handle overclocking (worst case scenario) without the psu shitting on the load. Secondly I wish to know if the motherboard supports crossfire( I believe it does, but I need to make sure) and if the two gigabytes are a good choice.(Not the 6870's, I'm going with em, but the oc gigabyte editions.) Will my power hold, will my rig work to play most games, is all my hardware compatible and what will my oc options be with my power supplies.I would also appreciate a few links and a minimum system power requirement for my rig.Please answer all my questions fully, and I thank you all in advance.

 

[Griffolion]

If your power supply is coolermaster i would be sceptical as to the reliability of the power delivery. Try going for a PSU along the lines of Corsair (HX), Antec (TruePower), Seasonic (X Series) or Silverstone (Decathlon). Considering you wish to overclock, you want to be at least 850W to stay on the safe side.

And yes, that motherboard will crossfire at x8x8 mode, so you're fine.

 

[ram1009]

You can never have too much power. Stressing a PSU is a gross error. You're going in the right direction and are far ahead of most builders who usually ask how small a supply they can get away with.

http://www.realhardtechx.com/index_archivos/Page2679.htm

This is a site that will help select a quality PSU. Bigger is always better.

 

[ko888]

The GIGABYTE GA-Z68X-UD3P-B3 motherboard specifications state :

Multi-Graphics Technology : Support for ATI CrossFireX™/NVIDIA SLI technology
* The PCIEX16 slot operates at up to x8 mode when ATI CrossFireX/NVIDIA SLI is enabled.

I recommend that you stay away from Cooler Master GX Series power supply units as they tend to suffer from mediocre voltage regulation, poor electrical noise suppression and poor ripple suppression.

As for the Cooler Master Silent Pro Gold 800W RS-800-80GA-D3, Hardware Secrets test review conclusion was "Noise and ripple was always higher than we’d like to see in a supposedly high-end product."

From AMD's own website:
See the second item in AMD Radeon HD 6870 Graphics - System Requirements

What's missing is the power supply's recommended minimum combined +12 Volt rails' continuous current rating. I consider this specification to be vastly more important than the power supply's total wattage.

For a single Radeon HD 6870 graphics card system the power supply should have a minimum combined +12 Volt continuous current rating of 24 Amps or greater.

For a system with two Radeon HD 6870 graphics cards in 2-way CrossFireX mode the power supply should have a minimum combined +12 Volt continuous current rating of 37 Amps or greater.

The power supply must also have at least four PCI Express supplementary power connectors to meet your particular needs.

The following reputable name brand power supplies will more than meet your needs :

Antec EarthWatts Series EA 750 - EC
Antec EarthWatts Series EA-750 Green
Antec High Current Gamer Series HCG-750
Antec TruePower New Series TP-650
Corsair Enthusiast Series CMPSU-750TXV2
Corsair Professional Series CMPSU-650HX
Corsair Professional Series Gold CMPSU-650AX
XFX Core Edition 650W P1-650S-NLB9