Adding Switched Rear Speakers to Pontoon Boat

Looking for advice on adding rear speakers to my pontoon boat.  I have 6 6.5" infinity speakers (4 in the main boat and 2 facing out the back toward the swim platform).  I wired the 4 main speakers in parallel to the two front channels of the amp and the rear deck ones to the rear channels. I used a carling style DPST switch in my console and ran the negative wire for each rear speaker through it after the amp, so basically they are on or off with this switch.  This worked great until my amp went out.  I am not sure if my set up caused the amp to fail or it is just a crappy amp.  It is a little Clarion XC-1410 that says that it is 2 ohm stable but did seem to get pretty hot while running, so I am unsure if my speaker switch may be causing stress or if there is a better way to do it. In a perfect world, I would like maybe two switches to turn both sets of speakers on/off independently of each other.  I know I could use the fader on the head unit to do this but that requires navigating through about 10 menus with one knob that my gf and others can't seem to grasp.  The goal was to have music out the back while swimming etc. without having to blast the people inside the boat, and to cut the rear ones off when travelling down the lake to aviod being a noisy nieghbor. Any information would be appreciated and I am looking at replacing the amp with a better quality unit but would like to avoid killing another one if I caused it.  Thanks to all, this is a great website.