I owe a long overdue followup, and thanks to those who helped me in this thread several months ago.
The small cruise boat install ended up going very well.
For about $1500 in parts, I was able to put in 8 outdoor wall mounted speakers on the top open-air deck, and 10 ceiling mount speakers in the enclosed bottom deck.
Used Berry to save $ .....a $260 SN2408 paging mixer gave ducking inputs (3), variable ducking level, mono summing for 2 ipods, and overall volume and tone controls. Didn't use its integrated 70wamp.
A 3000dsp inuke gave speaker zone control, eq, and limiting.
A bit kludged maybe, using the amp gains for zone volume control, but the crew on boat follows it easy enough....
I intended to 70v the speakers with a 6000dsp (to get the necessary voltage per channel or rather per deck) , but found the wall mounted speakers really sounded better using their 8 ohm setting that bypassed their tranny taps.
Since decent size wire was more or less in place, I just series/paralled speakers on each deck to bring load to around 4 ohms per channel, and was able to drop down to the 3000 amp.
All in all it was a great leaning experience, more importantly with happy results.
Thx again for the help! Mark