speaker hookup

I am installing two pair of Alpine speakers into my boat (wakeboard tower).

The speakers are SPS-170A and SPR-174A.  I am running them on an old Sony XM-3040F.  My question do I bridge the amp and run each pair at 8 ohms or just run each one on a separate channel.  My speakers cans hold a pair.

I would like to run as few wires as possible up the tower, but I obviously I want to get as much to the speakers as possible.  The amp is suppose to run 30rms @ 4, and 40 @ 2.  The speakers are not power mongers, they are recommended for 40 rms, part of the reason I bought them. 

Although the SPR's have their own crossover, I am also using an XM-3 Coustic crossover to filter out some of the base, what is a good crossover point for both speakers since the crossover has to be the same for both (one of each in the cans).

Most of my music doesn't contain a big bass element, but  I am also installing a small JBL GT650T sub with its own amp (Pioneer GM-X252) so it will have around 100rms.  I just figured the more bass I cut, the more power I can focus on a clean higher freq signal, which is where my music is.  I have read that most of the power is used under 300, so that is about where I had thought about cutting it.

I have three outputs on the crossover and headunit (frt, rear, sub).  I had thought about crossing the 170's (non-component) at around 1k, then crossing the 174's at around 100-150, since they have an external crossover they can handle the bass better than the co-axial 170's.  The only problem is that I lose my ability to fade front to rear (tower to the interior) because I would have the tower running on both front and rear channels from the headunit.