Incorrect on Intel being your only choice, they DO make modern ITX boards for AMD. The problem is that they don't make AM3+ boards in ITX format, the probably reason being power draw. Most AM3+ processors are 100W+ processors and that's a lot of power for a small board.
The do have some AM3 boards (Jetway and some company named Giada), problem is they won't support the FX-8000 series.
If you were instead to go with a FM2+ APU, they make several for the AMD A10-xxxx series, ASRock FM2A88X-ITX+ is one, Gigabyte GA-F2A88XN-WIFI is another. Of course, that would require a different processor, but the AMD APU's have much better integrated graphics.
You asked about a small form factor GPU, IIRC Gigabyte also makes a GTX 750ti low profile card which is pretty decent, only issue is it recommends a 400w PSU.