Mini ITX powerful gaming rig?

Yes, that will perform just as good on an ITX board. But in a tiny case, you will be fighting heat constantly. The card and CPU will be much hotter than in a conventional case with good air flow. What Mini ITX case did you have in mind?

You may want to consider a slightly larger rig, maybe move up to a mATX board and a case like this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Still small and transportable, but much better air flow.

Don't get that PSU. CM GX aren't reliable units. You'll do fine with something like SeaSonic S12II 520 or the slightly higher power, better voltage regulation and more efficient SeaSonic G Series SSR-550RM

The last mini ITX rig I built used this case:
http://www.newegg.com/Product/ProductList.aspx?Submit=E...

The 80 plus bronze PSU is included in the case. The 80 plus gold one is a direct fit as well. I bought the 80plus gold PSU and resold the bronze one that came with it.

You will probably want to ditch the HD7970 for something less power hungry, such as a GTX660ti. I'm definitely not an nVidia guy, but in this case it is your best option by far.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

One other thing to consider is the length of the card, this one is 7.53 inches. The Zotac AMP! is the shortest 660ti available currently. The max that case can hold is 9 inches.

Another thing you will have to worry about is your heatsink for the CPU. You will definitely not be able to OC in an ITX case on the stock HSF. I used a the much less flexible H60 when I did this a little over a year ago. However, the new H60 has much bendier pipes running to the block from the radiator which should make everything MUCH easier:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Other things you will need to worry about:
-Slot-Load or Laptop Style Optical Drive (either way you'll need a mini sata adapter)
-If you mount the H60 in this case you will have to remove the HDD tray in the front (just drill out the rivets). I used "double sided mounting tape" to secure an SSD and 750GB 2.5"HDD (a 3.5 inch drive will actually fit sideways against the right wall of the case, but you'll have to rig a way to make it stay without resting on something it shouldn't).

Lots to think about if you want a high powered ITX gaming rig.

All depends on the size of your Mini ITX case
I'm a huge fan of the Bitfenix Prodigy, small case with lots of room
I have a i5 in mine with a CM Hyper 212+ heatsink as well as a HD5970 (one of the largest and power hungry cards made)
No heating problems at all
easy and portable

The Bitfenix Prodigy is HUGE for an ITX case....

I was looking at the Cooler Master Elite 120 Advanced - Mini-ITX Computer Case with USB 3.0 Ports and Long Video Card Support. I will start looking at micro ATX cases and mobos though. Thanks for the suggestions.

Product Features:

- Unprecedented airflow for a Mini-ITX case
- 1/3 the size of a standard case
- Supports standard length ATX power supplies with an innovative rear mounting system
- Supports ultra high-end video cards (HD 7990/GTX 690)
- Stylish aluminum front panel
- Features a full size 5.25-Inch drive bay
- Supports up to three 3.5-Inch /four 2.5-Inch HDDs/SSDs (converted from two 3.5-Inch HDD bays)
- USB 3.0 Super Speed support

The CM 120 is a nice inexpensive case for building a miniITX gamer. But it needs more ventilation. I built a gamer awhile back with that case and had to add another 120mm fan on the drive cage to keep the stock A10-5800K within specs gaming. There is only about 4" or so for a heat sync/fan.
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As you can see, I finally had to swap the stock cooler for the beefier Phenom II X4 cooler w/heat pipes to keep temps down. By the time I installed the HD 7850 2GB card, it was quite toasty in there.