Mach 460 front woofers cutting in & out

I searched the forum, but couldn't find an an answer to this. I've got an 04 GT coupe w/mach 460 sound system. I blew my passenger side front 5x7. I had bought a Infinity 6820cs component speaker set (Infinity Reference 6820cs 5"x7"/6"x8" component speaker system - Features & Specs at Crutchfield.com) to replace the speakers a while back, but never got around to installing them. After installing the aftermarket 5x7's, the replacement speakers cut in and out. The volume is only about 1/4 of the max volume. When I bought them, the rep at Crutchfield assured me they were drop in's and I wouldn't have a problem. I've read conflicting info over the net as to what will work and what won't. I've read that the mach 460 speakers are 3 ohm, 6 ohm and 8ohm?? I know the aftermarket's are 2 ohm, so could this be the problem?

All the wiring is factory and the new speakers came with factory connectors. I didn't have to splice any wires when hooking up the aftermarket speakers. The factory speakers were working properly (except the blown speaker) prior to taking them out. The speakers pop slightly prior to cutting off, then come back on for a few minutes. The cutting on and off repeats. It only seems to become a problem, when there is bass present in the song. Maybe the amp is going into protection mode due to the load presented? If so how can I get the ohms where they need to be.

Bottom line is I'm frustrated and need help!! Thanks in advance for any assistance.