I can't imagine the usefulness of the front facing speakers. You would just be blasting music to fellow boaters and not to anyone in your crew.
The other boaters generally have their own music going, and prefer their own tastes in music.
In regards to whether your riders can hear the Kickers behind the boat, you might explain which ones you are looking at and how much power you plan to feed them. Some of the set ups on boats I ride behind can be so loud at 70 feet behind the boat that you are literally signaling to turn it down! Admittedly, they run a lot of amplifier. Loud is good but you want to be able to hear yourself think!
Try posting the model and power and I'm sure some folks on here can provide some insight.