Aftermarket stereo with factory Bose system question

RT2012z

Seeing as I've received three different answers from three different install shops hopefully someone here can clear things up for me. I have a 2012 Z with touring package/BOSE audio system including BOSE subs. I plan on putting a Kenwood Excelon DNX691HD stereo with an idatalink Maestro RR interface in. Here's the question...........

Will I still be able to use the BOSE speakers, subs and amp with the aftermarket Kenwood? I realize that I will have to buy a different harness but the thing that scares me is that one shop told me that 'until they get the factory stereo out and see what's going on' they can't give me a definitive answer and furthermore said that there's a chance that in order to use the Kenwood/Maestro I will have to replace all of the speakers and any BOSE components.

That's not an option financially and I don't want to buy a $700 stereo only to have it not usable unless I replace the speakers as well. I've researched the Kenwood and Maestro and know that those are compatible with my Z but its the speakers and amp issue that has me concerned.

If anyone here has a similar aftermarket unit combo and can tell me what their experience was, good or bad or if everything should be okay with the factory speakers it would be much appreciated, thanks.