Newbie to the forum. Hope I can help out sometimes.

The peak rating of an amplifier is what the amp can provide in short bursts. Like for a sudden bass hit. The RMS of the amp is what the "continuous" power output the amp can provide over time. The true RMS and the Peak value of amplifiers is related by the square root of 2 (or .707). You can find the RMS value of an amp by multiplying the peak power by .707. The peak power of an amp can be found by dividing the RMS value by .707.

You are correct about the matching of the RMS values for amps and subs. Matching both the RMS values is ideal, but if you have to fudge, it's better to go with a higher sub RMS value than the amp rather than the other way around. Will help to keep your equipment in good shape.

Mish