Go with the Polk mm651um components with 160watts at each. From the Boss
http://www.sonicelectronix.com/item_21823_Boss-PH4.400.html for the dollar and output I have been very happy with the cost to power to sound quality. And for less than $100 in a boat it can afford to be replaced every few year if it dies. My amps are in a dry zone so should last a while. Not the top of the line by it is an open air boat so you cannot deep the benefits of the high high end that I would run in a car.
I also have a 12 in a sealed box and a 10" bazooka and this total combination has proven to blast clean clear audio.
I have 3 batteries, 2 are isolated from the dedicated start battery, the dual group 29 deep cycles for the stereo last and last.
One thing to think about is if you have higher power amps than you intend or need to be delivering to the speakers then you will be operating the amp at a lower % of the max capabilities thus using less power. This is something to keep in mind. Me pushing 75w out would be way less power consumed than an amp that maxes at 75x4. More efficient use of battery power.
And trust me when I say that you cannot stand in my cockpit when I have the head unit turned to 50% or your ears will hurt. If that tells you how loud these speakers can be.
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Not Penny's Boat
1993 190 Horizon 5.0L EFI http://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=111361977 14' CMF Skiff SOLD
2015 Emotion Stealth Angler 11