If I make a couple of conservative assumptions about your speakers and room:
- speakers require around 1W to reach 82dB/1m (based on 2.83V/86dB/3Ohm)
- critical distance in your room is around 5 feet (in most domestic rooms it is less)
You will achieve 83dB RMS (my definition of “moderate”, based on the recommended level for mixing/mastering) at the listening position with about 1.5W of input power. Assuming a 20dB crest factor (ie for more dynamic recordings), that would mean 150W for peaks of 103dB. You’d then want some headroom, say double or 4x the power required for 103dB peaks, which would get you to wanting about 300W or 600W (although the speakers may not be capable of handling this much power).
Also note that I’ve made quite conservative assumptions here, basing the numbers on a higher than typical critical distance and the lowest impedance of the speakers.