Onus :
There is nothing "crappy" about the HD7970, referred to by HardOCP as almost a waste for single-monitor 1920x1080 gaming.
The concern I would have is over heat. Small cases do not get rid of heat well, and even if you keep your CPU and GPU temps within limits, other parts (e.g. VRMs, capacitors in the PSU) will be stressed. If you want a long-lasting mini-ITX machine that can play any game, I would seriously look to accept lowered settings in order to use less powerful parts that won't produce a lot of heat. Otherwise, move up to micro-ATX (which isn't too hard to carry) so you can better deal with the heat.
One 7970 is indeed very crappy.... WHEN YOU ARE SPENDING ONE GRAND ON A GAMING COMPUTER (ONE GRAND!). A gtx 770 is a better choice, or even gtx 680 in sli is better, or even 7970 in crossfire (note: even with amd's new drivers, nvidia sli is still better at dealing with micro-stuttering).
I already told you what I could do with 1 grand, and my pc would walk all over yours (in gaming frame rate performance). I am telling you to choose wisely........ if you care about having the FASTEST gaming pc that you can possibly get for 1 grand. Like, are you a gamer? Like I am confused here.
A 7970 is not "almost a waste" for one 1080p monitor. I am guessing you have never used one on battlefield 3, in Back to Karkland maps (like I have). Then there is Crysis 3. Then there are a couple of other games. But most games are a walk in the park for one 7970. This is not the point anyway, the point is getting the fastest pc you can get for 1 grand.