So..
1. I'm building a similar rig. Macbook air 11'', 8GB RAM, core i7 + Sonnet Echo Express Pro + GTX 660Ti.
2. Several points for the people who gave us the article:
a. Re power connector. Google "FSP Booster X5": Another 80$ and you can drive a GTX 690 in there. Nice, compact and sits right next to your sonnet:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817104054&name=Power-Supplies
b. Remember how they taught us all those years ago that the amount of RAM has nothing to do with how fast a graphics card is, and it's all about the GPU chip? Well, they were right.... as long as you can keep dumping new code and textures into your GPU with no impediment whatsoever.
Not so right when you have limited capability (read: thunderbolt) between GPU and CPU/ram, and the more you cache, the less you slow down to wait for stuff to come through the pipe.
For this reason, my rig will use a GTX 660 with 3GB. (I'm tempted to buy a 690 with 4GB just for the bragging rights of running one on my macbook air, but sanity seems to want to intervene).
c. Thunderbolt comes in two flavors - single-channel (1x10Gbit in each direction) and dual-channel (2 x same). Some elaboration please - did your equipment (motherboard, Sonnet) have/use one or two channels? My 2011 mac had a single-channel TB controller, whereas my current one has a dual-channel. Does the sonnet take advantage of the second channel or not?
Can I suggest you guys do a followup