Congrats on your M80's! Like others, I wholeheartedly recommend keeping them even if it takes you awhile to save up money for an appropriate AVR/amp to drive them. I personally had a bad experience driving M80's with an Onkyo TX-SR805, to the point where I returned the 805. The long version of that story is right here.

I am currently running my M80's with a Rotel RSX-1057 and it does a great job at it. The RSX-1057 may be a bit over your current budget, though when I was having issues with my Onkyo setup, Alan recommended Sherwood Newcastle, Denon, Harman/Kardon, B&K, Rotel, NAD, and McIntosh.

A: Epic 80 * 600 / Integra DTC-9.8 / A1400-8
V: Samsung HL-S6187W / Tosh HD-XA2 / PS3 / Oppo 970HD