i'm planning on getting a set of the pg rsd6.5 comps and i believe they're rated at 90 rms. i was wondering, should i be looking at a 2 channel or a 4 channel amp to power these? also they're rated at 90 rms at 4 ohms i think, so should i be looking for an amp that does around 90 at 4 ohms? it's a newb question, i know... but advice would be great. thanks.