Playing with this SoC
If you're simply interested in using a SoC processor that can run OpenCV, I suggest the Raspberry Pi.  There was just a new version released, B+.

It uses a  Broadcom BCM2835 SoC which includes an ARM1176JZF-S 700 MHz processor, a VideoCore IV GPU and 512 MB RAM, and also four USB ports (so generally you don't need an external hub for a keyboard and mouse), HDMI in several resolutions, audio (so-so quality), Ethernet, and a microSD card.

Debian and Arch Linux ARM distributions are available for download from the main site.

All this for $40 (plus cables and power supply).

Here's the official page for Raspberry Pi and OpenCV.

And here's a OpenCV project on the Raspberry Pi that does facial recognition.

So forget about going to the trouble of making your own board.  You could be running one of these tomorrow.