My boat came with a ZX700.5 amp in it. I am adding a 750.1 for my L7, and I want to keep the 5 channel amp for cabin and tower speakers. Can I run my polk 6.5 off of four channels and the 6.5 HLCD's off of the sub channel? All speakers are 4 ohm.

Nope, the sub chnl 5 of the zx700.5 is low-pass only. This would not be very good for your tower speakers.

That's is what I thought. Looks like I will be selling that amp and getting something else. That sucks! Something else I didn't plan on buying!! BOAT (Break Out Another Thousand), but I can't go without it!!! Thanks Mike.

Chris maybe think about buying an L5 instead. They are just right for those amps. If you build the box right it will sound great. You can get an L5 shipped for around $140 through sonicelectronix.com