Ah, I misunderstood. I thought "100" was the price you were wanting to pay.
Assuming the 65X were being used as subwooers, there's no reason you couldn't use a mono amp on them. Would make wiring a little easier and quite possibly could be cheaper aswell.
As far as the 65M, it depends on where you are mounting them. If one pair is going up front and one pair in back, I'd suggest a 4-channel to facilitate the ability to fade.
If they are both going up front (like two in each door), then a single 2-channel amp for those would work just fine. Or, a single 4-channel....two channels for the 65M's, and the rear two channels bridged to the 65X's (or you could just run two per channel aswell)
What is your budget (you have one, I'm sure you don't want to spend $2k on an amp...for example)? And how are the speakers being used/installed?
the 2 sets of xs are going in the back of my blazer and the ms are going in the front id like to keep it as cheap as possible but not have a pos amp/amps
i think a 2 channel would work for the front in 2 ohm at 200 watts and the back not sure on