I have purchased the 8 camera license and a banana Pi (http://www.bananapi.org/p/product.html) running bananian (https://www.bananian.org/download).
The difference of raspberry is that Banana Pi supports SATA drive!
You can move the rootfs directory as descripted here -> http://gleenders.blogspot.gr/2014/08/banana-pi-boot-your-rootfs-from-sata.html
Using some betchmarks from internet, banana Pi (I used m1 version) using SATA drive is better that Raspberry Pi ( more: http://www.htpcguides.com/raspberry-pi-vs-pi-2-vs-banana-pi-pro-benchmarks/)
Using 5 ip cameras I see that resources are high but are resonable.
A small wish list for developers:
1. H264 support for ARM
2. a banana/raspberry pi image optimised/pre-installed xeoma
3. a plugin to trigger GPIO pins of banana/raspberry