Don, if you don't have the manual or other info, the 7220 had a 20 watt/channel continuous power rating, but as was typical of NAD design at that time, had a dynamic power rating(to handle 20 millisecond attack transients of instruments)of twice the continuous power rating.
If it's in good operating condition, the usual situation applies: it'll provide transparent amplification within its power limits. For your bedroom situation it's likely that the moderate listening levels that you'll be using(even for that more dynamic classical full orchestral stuff that you'll be enjoying)won't exceed the capacity of the 7220.
