i just checked my title and oops my car is a 1996

I still dont understand why the factory amp was bypassed/

becuase the factory rear speakers have 4 wires going to them.....2 for the full range from the HU and 2 from the amp. All aftermarket speakers only have a + and - so its better having the power from the HU running the rears and getting fullrange that just getting bass from the back with the amp

They're certinaly not DVC (dual voice coil), atleast in the industries sense, but they are a two way system, sorta like a component speaker.

The woofer section of the 6x9 has it's own higher powered amp to produce more bass.

As long as you use a wire straight from your aftermarket head unit to the full range aftermarket speakers you should be fine. The tweeter/highs wire might do this, but the factory headunit/wiring might have a high pass crossover in it to cut out bass being made by the woofer section.