Do you have anything now? Your price range could do quite a lot. Check out some of my threads in the modify section. I would start with a decent head unit...budget about 200 for that. 4 good mid range speakers. I went with all Kicker speakers. The reason for that is there subs are awesome for boats. With the 10" subs, they are also free air rated and sound awesome just mounted in the wall of the boat...no box needed. So i kept with all kicker speakers. The mids run 80 bucks a pair. The subs were 90 each. I highly recommend polk also if you want another option. They run about the same for the DB series. So for 4 speakers and 2 subs...you are looking at about 340. As far as AMPS.....i honestly dont think you can find anything better than an alpine. They are digital series amps and run very efficiently and cool. They can easily power all 6 speakers with no problem. The pdx5m runs $430. So for the head unit, speakers and amp you are at around $975. That leaves you the rest for wiring and a remote. All of that stuff is marine rated. You can buy any brand you choose, just make sure all components are marine rated.
If you have any questions about anything this is a good place for them. Myself and lots of other memebrs have done a lot of research and work on our systems. As far as needing speakers facing the rear...thats totally not needed. With the above setup....my boat rocks and you can hear it loudly 100 feet away. The remote on the swim platform really helps. I also have a RF based keychain remote that i can use while we hang out in the water.
