Sorry, I can't help you on that one. I have little experience with amps outside of my Lake People G109 but I can tell you it drives the 880s beautifully. I mentioned the voltage because I was hearing a lot of people saying the 770/880/990s do best with lots of voltage but I wasn't very impressed with the voltage and power specs on most amps. The G103 has nearly as much power and voltage as the G109 which is a lot more than most similar amps out there.
Here's the G103/G109 thread BTW:
Its not terribly active but I'm sure there's at least a few people around here that have the G103 and have experience with the O2 and/or Matrix. I know there are several others that have the G109 and its quite similar to the G103. Anyway, good luck. If you end up with the G103 I'm sure you'll like it.