I think they ought to get their own set of channels from an amp. They'd need a HP crossover too. Not sure if the amp or HU would have that on it.

What I really think you want to try is moving the MBQ tweeters up there. You might not even have to run new wires. Just pluck them from their current location and put them where the Kickers were. Where exactly are they now? Both sets, that is. I don't know where stock locations are for you. The tweeter may not be right on the mid. It could be up higher in the door. Usually stock tweeter locations are terrible.