750W or 850W?

I am looking for some some advice on a power supply that is good for my upcoming build. I currently have the Corsair Enthusiast TX850M added to my order, but since my CPU is on backorder, I have some time to rethink things. The calculator at http://www.extreme.outervision.com/PSUEngine shows that I need well under 850W for my design, but it doesn't take into account things such as potential video card or RAM overclocking. My build is as follows:

Case: Silverstone TJ08B-E mATX
Video Card: EVGA GeForce GTX 690 (single card, I want to account for potentially OC'ing this slightly)
CPU: i7-3930K (With interest to overclock it likely as far as 4.3 GHz, but 4.5 and 4.6 seem to be fairly common for this CPU so I want to keep that open).
Motherboard: Rampage IV Gene (mATX x79 board)
Boot HDD: Crucial SSD 256GB M4 (with potential for a 2nd in the future)
Main HDD: Seagate 3TB Barracuda 7200 RPM (I want to leave open the potential of sticking in a second HDD in RAID in the future)
RAM: Corsair Vengeance LP 16GB DDR3 1600MHz @ 2x8GB (for the potential of OC'ing all 4 DIMMs @ 2133 MHz)
Optical Drive: LG CH12LS28 Blu-Ray
Cooling system: Corsair H80 (although I have been considering the NH-D14 but it gets very close to the 690 in this case on the mATX mb)
PSU chosen: Corsair TX850M


Other information that may be useful:
- I may use several USB slots at once (I have 5 external HDD's and I sometimes have 2 or more plugged in at once including 3.0 USB, laser mouse, keyboard, flight joysticks & yoke, Astro Mixamp, charging my phone, etc.)


Cost is a thing I want to consider. I chose the 850W because it is far more than I was getting on that online calculator (719W recommended). I chose many fans, USB, multiple driver, OC'ing, and other things to get there. Despite this, 750W just doesn't seem enough. I have been looking also at the AX850 and HX850 by Corsair. The prices I will pay for the 850W by Corsair (in Canada) are:
- TX850M: $112.49
- HX850: $149.99
- AX850: $168.49

I am open to other brands, but most people seem to use the Corsair brand so I only focused on those. The current models of the HX and AX are Gold rated. They both look fairly modular. I realize the AX model is made by SeaSonic and the HX by another company, CWT. Is the AX really worth $60 more than the (semi?) modular TX850M? What is the difference between the performance of the HX and AX? All I have learned from other topics is that the AX is quieter due to having a better fan setup.

Thank you in advance.

Thanks for the quick reply. I used the maximum USB slots to account for the possibility and I used a 250W LED fan since the front fan is 180mm and in case I added 3 fans in case I used the NH-D14 instead of the H80 (I understand the error this causes since it would account for 2 cooling systems at once, which I won't have). 550W seems very low since nVidia recommends a 650W for it.

The 3930k had a load of 516W @ 5 GHz (far higher than I would need) with a 580 GTX at this website: http://www.tweaktown.com/reviews/4435/intel_core_i7_3930k_lga_2011_cpu_review/index2.html. This and your information make me feel that 750W might be more than enough to power this computer.


I keep seeing countless 3930k + 690 GTX builds with 1000W or 1250W PSU's like this one (http://pcpartpicker.com/b/wU5) and it makes me think 750W or 850W would have been too low. I guess with all of the people buying such huge PSU's, it makes it hard to know what is what. Coming from a notebook, I have a large lack of information on this.
Edited by baconcow - 8/21/12 at 2:28am

This is all very interesting information. Since I am having the computer built at the store (since it is being shipped and I prefer the testing of hardware they do), I suppose an experienced builder would raise a red flag if it is not enough. Looking at the 750W PSU'sm the HX is only 109.99 and the AX 142.49. This is considerably less than the HX and AX versions of the 850W and I wouldn't have to add a lot of money to my order ($30) to upgrade to the AX750 (would cost me less to use the HX750W).