Just my 2 cents worth here. Regardless of what power supply you get I'd strongly recommend getting one that is totally modular. Reason being if you don't need to connect a device to the PSU then you don't have to figure out what to do with all the extra wiring.
Makes for a neat and tidy case. Helps with the air flow also if a bunch of unused wires are not in the way. Not going against what PP said but a little lea way in the PSU will let you add more goodies with out having to swap out the PSU later.
I would also venture to point out you like me, are investing a chunk of change in some thing you want to last a good while. Power surges such as those from thunder storms, will make short work of a computer system. Unless you have home owners insurance, if you get zapped you're just out of luck. Therefore I'd recommend getting a good UPS with solid surge protection. I use the APC brand because it's a solid brand name with a good track record. I have the APC BE750G Back-UPS 750VA 10-outlet Uninterruptible Power Supply (UPS) - Newegg.com
. Inexpensive insurance.