That Pioneer isn't really 140 watts per channel so you'll be OK. It is probably more like 60 watts per channel into 8 Ohms with all channels driven. The back panel on the Pioneer doesn't lie. It states power draw of 415 watts. 415 / 5 channels = 83 watts/channel. Then you have to factor in the inefficiency. Not sure what class the Pioneer is but Class A/B is around 65%, Class H about 80%, and Class D about 90%. If it is Class A/B, which is typical for receivers, then that is 83 watts/channel x .65 = 54 watts/channel. 2 channels driven would be a different beast and depends on the heatsinks on the two channels being used. I'd say you're probably good for 100 watts x 2 into 8 Ohms. Receiver manufacturers, by US law, HAVE to state how much current a receiver will draw on the back panel for safety reasons. THAT is the FIRST place I'd look to determine the power output of any receiver. The specs printed in the owner's manual or product sheet are mostly made-up numbers.