I thought that MediaCenter could only handle 4-Analog, 4-SD, and 4-HD tuners for some reason. Are you sure that it will support 8 HD tuners at once??
Tuner Salad is your friend.
Actually, it's not an issue of SD and HD. The tuner types are NTSC, ATSC, and QAM.
I have an amp in line; I've had it come unplugged and cause problems back in the analog days, and just a few weeks ago when I couldn't get a couple of channels at all it turned out that the previous tech 5 months prior had routed around it and it wasn't inline anymore. New tech put it back inline, and all problems are solved.
No idea why the no-amp situation worked for a few months and then stopped, but you know the cable company--they're always working on things and switching them around.
Hang onto that amp. If you needed it once, you'll likely need it again.
Does ImTOO integrate with 7MC?