I had the exact receiver driving my M80's and the power on these is legit. They are actually very much in demand due to the power they have because the newer receivers are not built like this one is. I would try for both upgrades but if I had to do one or the other in your situation I would do the sub.

http://www.soundandvision.com/content/de...I9LgGDMxeiA5.97

his graph shows that the AVR-3808CI’s left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 186.7 watts and 1 percent distortion at 210.9 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 238.9 watts and 1 percent distortion at 277.3 watts.
Read more at http://www.soundandvision.com/content/de...lfzcZ2KlLsqR.99