No, I would just use the factory amp to power your speakers. Even though the HU says "50wx4", you'll only really see around 11-24w. Just an FYI, the rear outputs of the factory amp are separated. Low/mid range goes to the 6x9's and high range goes to the 4" speaker. So if you put in a 2way or 3way 6x9, you're only using the woofer of the 6x9.