Welcome Jailbreaker!
I briefly demoed a pair of Jamo C807s many years back. While I did enjoy how they sounded I ended up returning them because they were not magnetically shielded (this was when I still had a CRT TV).
Did a quick search on the Jamo 507 and as far as specs go, the M80s will play lower. Sorry, I can't offer any kind of direct comparison, but like Mark said, the M80s are very accurate and revealing. I've listened to another member's M80s (grunt) and they are a very complete speaker from top to bottom.
Oh, and the QS8s are really outstanding surround speakers!
