In the Donzi I have 12 JL M770 (7.7" components) and 4 JL 10" marine subs. I went with 2 900/5 amps for 8 speakers and the subs and a 600/4 for the remaining 4 speakers. It sounds great and is very loud but I do regret not going with separate amps for the speakers/ subs. While my configuration is better on the batteries (I have 2 group 31 Odyssey marine batteries dedicated to the stereo). Looking back, I should have went with 3 600/4 for the speakers and 2 600/4 for the subs. Really really wish JL would come out with a marine HD 6 or 8 channel amp that pushes 150w rms per channel. Would only make sense as boats typically have quite a few speakers.

Im not getting too carried away. The boats only 22 x 7 there is not a lot of room for multiple amps etcs and I don't need to hear it 3 states over. Just need to have decent tunes when cruising.

A 5 channel keeps things simple...Alpine makes a nice one, I have one that came in my boat and it is a very clean amp. A digital amp for your subs would be more efficient but if you have 2 or more batteries does it matter?

Massive

Alpine PDX V9. 4x100 and 1 x500 watts of clean power
Its a class D digital amp.

JL audio 9005!!!! Ftw!!

Memphis marine has been great for me this season so far

What are the RMS ratings on your speakers and subs?

If it's not going to get "wet" then the Alpine PDX Amps are hard to beat, they are compact and reasonable to buy, especially used. JL makes AWESOME stuff, but, it's pricey.

I guess it's all relative, if you have 300-400K in a boat then dropping 10-20K on a stereo is small change, but, in a small boat like mine it would be a bit excessive.