Someone help me with boat audio

Ok so i see the threads go by with all these speaker names like wetsounds etc...We are getting a tower for our boat and i am going to redo all of the audio. I had a friend help me with all the stuff for my jeep from head unit to subs, so i guess my question is "is doing the audio for my boat any different than for a car?" Also what speakers, amps, subs, and head unit do i get? Are the big name brands such as wet sounds that much better or would i be ok running 4 kickers across my tower? Let me know the best brands if you can so i can keep an eye out for deals and such. Thanks guys