I agree with TLS--you have come up with a bad idea for many technical reasons!
Furthermore, you don't want to pollute the excellent GE speakers with crap Aiwa speakers!
If you want all speakers driven, then look for some "7 channel stereo" or "all speaker stereo" or "party mode" setting, or whatever Yamaha calls it (my Pio calls it 7 channel stereo). In other words, your BEST option to do what you want to do is to indeed use the DSP settings on the AVR.
Now, whether or not your goal is a good idea, that is a different question.
And, why front presence speakers, but no surrounds????