After swapping out all the speakers (4 doors and 2 R/L front dash speaker), I want to drop in another 4" for the middle front dash. This is on the 07 Tundra non-JBL system. There is an empty space there on non-jbl system and I have a pair of extra 4" I'd like to use...

Can I just wired in parallel to one of the rear door speaker wire like the way stock wire the 3.5" dash speaker parallel to the front door speakers? If so, this will only be ONE thus either tap into left or right rear speaker..will this make it "imbalance" and screw things up somehow?? Please note that I'll swap out the head unit to Eclipse avn 5510. Speakers will be powered by this head unit.