What is the main usage of this PC? If Supreme Commander if your main deal, yea you want a quad. If using AI (or Sorian AI specifically) at large amounts it eats CPU for breakfast due to horrible code and optimizations. One of the serious fall backs of the game and why it never took off in 2007 where single core CPUs dominated the mainstream market.
I say everything looks good, but an mATX build will still be about as heavy as a mid tower. The only real difference here is cooling. The Sugo cases are great, but the cooling not so great unless you have one of the latest ones.
I'll also say, that if this rig is geared towards gaming then 8GB will be plenty.
For the price, get the 3570k instead. I think it's only 10 bucks more and much faster than the 2500k.
The motherboard makes getting a K series CPU pointless. You need P67/Z68/Z75/Z77 chipset to overclock a K series. Save money and get a better board.
Newegg.com - ASRock Z77M LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard
The 660 is a very good card for the price. I wouldn't change that. The SSD on the other hand, kind of small.
Yea you can fit a standard sized PSU in that little case, but you would probably be better off with a modular setup due to airflow restrictions in an mATX case. The Corsair 650HX is kind of pricey but a good option.