The perfect amp for this situation would be an Audison SRx3. It has 2 stereo channels and one sub channel, all channels are 2 ohm stable. I agree with what the others are saying too, turf the 6x9's, they are a waste if you already have a sub. Get yourself a nice set of splits for the front of your car and run them off the amp.
The amp has several different configurations that can be used, the 1 or 2 best suited are
2x75wrms + 1x250wrms @4Ohms or
2x65wrms + 1x340wrms @4/2Ohms