How to wire 2 sony 4 channel amps

Hi, i recently bought 2 sony amps...they are both the same.......4 channel 55x4 rms.  I have the sony xplod head unit and it does have front/rear/sub output.  I want to amp up the front door and rear speakers with one amp. Then with the second amp i want to amp up 4 additional 61/2" speakers i recently bought.

I know how to split the power and ground but i am not sure about the signals. If i use the front and rear output from the sony headunit for one amp to power door and rear speakers.......what signal do i use for the additional speakers i am adding????? 

Are the 4 additional 6.5" speakers in the rear of the vehicle? If so, I would use a Y-cable (something like this http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=181-690) to split out your rear outputs. Your other 4 channel amp should be able to take one set of inputs to source all 4 channels. This will eliminate the cable clutter and complexity and should not matter since all 3 sets will be in the rear of the vehicle.

Thanks nouseforaname!   I was reading that by taking a single front preamp output at the headunit and using a Y adapter actually cuts the signal in half reducing the quality of the output thus affecting sound quality!! Not sure if its true thats why i was asking the best way to set this system up. 

I was thinking ....since i am adding the 4 extra sony xplod's 61/2's in the rear hatch of a honda crx which has no back seats from the factory , i could move the speakers from the factory rear location and move them up front! This would sound better and allow equal fade because i would have 4 speakers up front and 4 in the rear thus allowing me to do what you said about having one amp on the front outputs using 2 "Y" adapters  and one amp on the rear outputs using 2 "Y" adapters. How does this sound to you?