So I have a Kenwood DMX4707s Headunit. I’m pretty sure it’s only 4 channels. I have Alpine S2 6x9 2-Way Coax’s in the front and Kicker KS 6 1/2 2-Way coax’s in the rear. Should I just get a subwoofer and remove the Rear Speakers and bridge the two rears to the sub for a more balanced sound? I feel the 4 door speakers can hit mid-bass but when listening to rap they sound like crap. The door speakers are not amped right now either and I want to Amp them. Do I need to get 2-Amps separate for the Door Speakers and Sub? I’m probably only going to get a single 8” or 10” sub with a Slim enclosure as I’m in a 2016 Nissan Frontier King Cab which is a pretty small cabin. Not a major bass head but I feel like I would appreciate some low-end bass with certain music. Also, if I want to re-attach the rear speakers WITH a sub in the back, I would have to get a 5-Channel Headunit? I’m assuming there’s no way around it?