First, can we assume you are using the crossovers built into the speakers? That seems reasonable. If this is true, then it is no different than any other speaker, you send full range, and the passive crossovers in the speakers sort it out.
However, if you don't have pre-amp outputs on at least one of the amps, there is really no way to synchronize them.
In my case, I have an Onkyo TX-8255 (50w/ch) and a Yamaha RX-797 (100w/ch). I only need one for music, but I like to run them both for movies. The Onkyo drive two 12" three-way speakers, and the Yamaha drives two tower speakers with twin 8" woofers each.
That is different than what you want to do, but the principle is the same. I pre-amp out of the Yamaha into the CD input on the Onkyo. Then I play some music, and BALANCE the speakers by bringing the volume up on the Onkyo until it matches the levels of the Yamaha. FROM THAT POINT ON, volume and tone are controlled by the Yamaha. The Key Point being that the Yamaha controls the volume for BOTH AMPS, and the volume of the respective amps stays synchronized.
Now, you could simply split the signal from your Player and feed both the Integrated amps you have, but how to you keep the volume balanced. If you raise the volume on the amp driving the bass, then you have to re-adjust the volume on the amp driving the tweeters. This is not a very smooth or accurate process.
There is a microscopic chance that a single remote control will control both amps simultaneously, which would be sweet if it worked, but I'm not so sure it will.
To really make this work, one amp has to be the master (Pre-Amp Outs) and the other amps has to be the slave. Other methods might work, just not very well.
Steve/bluewizard