I have a 1999 f-250 powerstroke. It is loud in the cab due to being a manual. Currently I have 2 front 6x8s and spots for 2 back 6x8s and a clarion headunit with full outputs. I was planning on putting in a 4 channel amp and new speakers to help just get more power to the system. I have a 4 ga power wire in the back for emergency lights, sirens and radios, so I can use that since the stereo is turned down during calls. What are some good 4 channel amps for decent money? Also what brands do I need to stay clear of (I shop pawn shops alot, this is more useful)? What kind of power should I look for? How many watts max with my current power setup?