Philip, welcome to Axiom. Although the total volume of a listening room is of some significance, by far the most important factor is the distance of the listening position from the speakers. A room doesn't have to be "filled" with sound at the level which is satisfactory where your ears are.
Since the R-S700 is a stereo receiver, it's unclear how you would be using four speakers, but it can be said that the 100 watt rating it carries should be fine to drive speakers of average sensitivity(such as the Axioms)to plenty of listening volume at typical listening position distances on the order of 3-4 meters.
