I am getting speakers of varying impedance (M60's, a VP150, and QS8's). I would like to know how this affects the demands put onto the receiver. Does a receiver rated at 70 watts driven into 5 channels at 8 ohms have sufficient power to drive the above speakers in a room that is 23' x 18' x 8'? This is my specific question - my more general one is what sort of demands do speakers systems of varying impedances place on a receiver - where exactly is the heaviest demand and how does it affect the system as a whole?

Thx in advance

Ed