750W Modular PSU needed.

Solution
If not too late I recommend the EVGA model linked by "bignastyid":

- reasonably priced
- great customer feedback at 4.8 of 5 average (62 reviews)
- 10 Year Warranty for labor/parts

- supports C6/C7 power state for Haswell

*If the Power Supply doesn't support the Haswell spec specifically for C6/C7 then the computer may crash when coming out of the low power state. The workaround is not to use that particular low power state but that's not ideal. Just a heads up to avoid any PSU that doesn't have this.

Should say something like:
"Ready for 4th Generation Intel Core Processors (C6/C7 Idle Mode)" (or mention Haswell instead of "4th gen")
Other build points:

1) Recommend the Noctua NH-U12S instead. Slightly more expensive but much quieter under load (silent in idle even if only fan in system).

2) Windows 8.1 64-bit OEM:
There's no great reason to choose Windows 7 and many reasons not to. You can get START8 for $5USD to make the interface work like Windows 7.

Reasons for W8 include:
- better security (can prevent boot-time viruses)
- better memory management
- new gaming features won't support W7 (shared tile resources)
- BF4 works better in W8 (due to code to support improved core management in CPU)

And several other reasons.
 
If not too late I recommend the EVGA model linked by "bignastyid":

- reasonably priced
- great customer feedback at 4.8 of 5 average (62 reviews)
- 10 Year Warranty for labor/parts

- supports C6/C7 power state for Haswell

*If the Power Supply doesn't support the Haswell spec specifically for C6/C7 then the computer may crash when coming out of the low power state. The workaround is not to use that particular low power state but that's not ideal. Just a heads up to avoid any PSU that doesn't have this.

Should say something like:
"Ready for 4th Generation Intel Core Processors (C6/C7 Idle Mode)" (or mention Haswell instead of "4th gen")
 
Solution