The best advice I've ever seen on here is to upgrade in zones based on what you want and your budget. Most of what you hear comes from your in boat speakers. Get that part right, get the right amp(s) for it and make it where you can add on to your system. Your stock Kenwood in boat speakers probably should be replaced first. Lots of guys like the Polk DB series for what you get for the money. The next best advice is don't just put car door speakers in cans on the tower because they fit in them. You can't hear them at the end of the line anyway. Get the right stuff from Exile, Wetsounds, etc. or don't bother with the tower till you can do it right.