I would agree that it's not critical. It should be "close", but it doesn't have to be exactly matching. The speakers should also be "close", but doesn't have to exactly match.
In my opinion, the front 3 speakers (left/center/right) should match exactly both in speaker brand/model and amplifier.
Power does not have to be high. In real situations, you could be using 100-200 watts on the front 3 channels for explosive HT scenes. However, the surround speakers would really only be using 15-25 watts, maybe with extreme peaks of 30-50 watts (but that is going to be really loud!).