How many watts do I actually need?

Less than the marketing suggests, more than the minimum. The math: an 88dB-sensitive pair at ~2.5m plays ~78dB from 1 watt in-room, ~88dB from 10W, ~98dB from 100W — every +3dB doubles power. Target an 85dB average with 15dB of peak headroom and a typical room needs the ability to swing ~40–100W into 8Ω; the average draw at your seat is closer to 10W. Watch the 2.83V catch on 4Ω speakers: subtract 3dB to compare against true 1W ratings.