John,
You posted just a fraction before I did so I wasn't able to read your comments in time.

The Kicker 5-channel is probably fine and you most likely have a problem(s) external to the amplifier. If the amplifier does require repair and its not a water-exposure issue then its still worth it versus a replacement. That amplifier will have no trouble serving your purposes as you've described them for six in-boat speakers and one subwoofer.
I'm confident that if you do find another 250.2 then you will be set for tower amplification for the long term. But I am going to recommend that when the time comes you move to a single pair of larger tower speakers rather than trying to supplement your existing pods. From a power standpoint the idea of using dual 2-channel amplifiers in the bridged mode better fits a single pair of more substantial speakers than it does four speakers. And, two 8-inch tower speakers are going to have the advantage over four 6.5" conventional automotive-based speakers in surface area, warmth and midbass extension.

For now you will have to first track down the present demons and get the existing equipment operating at its potential just as MLA wrote.

David
Earmark Marine