New battery wiring with dual amp

[Dom08]

Hello all,
Looking for some information on the following:

1) installing 2 new batteries on my 07 outback. What cold crank amps should i look to put in? Boat will have 2 audio amps

2) how should i be wiring up the dual batteries to the bus bars in installing. I also have a isolator relay solenoid.

I am starting from scratch and not too sure which way is best to wire this set up i am trying to minimize the amount of connections on the batteries and use the bus bars.

[MLA]

For a cranking battery, get the most CCA or MCA you can get in whatever group size will fit. Odds are, you are working with group-24.

Are you going to be setting up a dual-bank system with a cranking bank and a house bank? If so, you will want a deep-cycle battery. So in this category, you would be looking at the battery's Ah rating.

^^^^ If this is the plan, then the batteries typically get wired to a manual dual-bank battery switch. Do you have a switch? and if so, what type?

[Dom08]

Which way to wire it, the previous system was hooked up as to batteries to isolating relay and everything hooked up to one particular battery well the other battery was hooked up to the motor. I had no switches or anything

[Dom08]

Would installing a battery switch get rid of the isolating relay?

[Dom08]

Picked it up,
Going to wire it up. Fuse between the battery and acr on both house and starter battery? What rating should they be?