The Clarion M309 combined with the Polk 651UM 6.5" coaxial speakers are a perfect match. Simple easy to use controls along with many ways to bring music into the boat make this an easy decision.
This combination without an amp supplies ample bass and plenty of volume. I was considering an amp but after hearing this not now!
I mounted the head unit in the bulkhead of our North River Seahawk aluminum fishing boat and couldn't be happier. The usb connection recognizes my flash drive immediately and the menu system is very intuitive and easy to learn. Great value and you will not be dissappointed!