I have new kenwood deck 50w x 4 , 2 rca output, 2 x 400watt kenwood 4 way speakers, and 2 x kenwood 200w splits, at the front. I will upgrade to amps and subs as required. The system sounds good just with the 4 ways, but obviously doesnt work well with all speakers wired to the deck. Should I power all speakers with amp, and what size? and power a sub or two with another amp, what size? Any other ideas appreciated.