Cam, first let me say that it's great that you and your sister are doing that for your folks. How're you gonna "surprise" them into that hall?
As to the sound levels, of course your equipment can "fill" the hall with some level of sound even at the farthest points. For example, if the farthest listener is about 40' away, rather than the 10' more typical of home listening, the level there would be about 6dB lower than at 10'. The RPA-1 would have a maximum output about 3dB greater than the 3801(double the power)and this would partly compensate at the farthest listening spot. My thought is if levels aren't to be employed which would deafen the guests(as well as your parents)your M80s, EP500 and RPA-1 would be enough to assure a musically enjoyable time.
