Just run all new wires. Those MB Quarts like lots of power Im running 100 watts to each one so I really doubt the stock headunit is gonna be able to push them very well. I recommend you get a nice amp to push them. Just my 2 cents, but I do speak from experience. I have always recommended not using the factory wires especially with nice equipment.
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Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.