first time wiring a new system

Definantly run the the 4ga through the firewall !   Do Not put a D-block in the engine comartment (lot's of problems).  Put an "in-line" fuse no more than 1-2 feet from the battery.  Run the 4ga as far as you can then go to the D-block.  Same with the ground, you want the ground D-block as close to the amps as possible.  Make sure you have a GOOD ground.  don't wrap a wire around a seat bolt.  You shouldn't need a cap.

Also, very important.  Run the RCA cables on the opposite side of the car from the power, remote, and ground wires.

Have fun.

Definantly run the the 4ga through the firewall !   Do Not put a D-block in the engine comartment (lot's of problems).  Put an "in-line" fuse no more than 1-2 feet from the battery.  Run the 4ga as far as you can then go to the D-block.  Same with the ground, you want the ground D-block as close to the amps as possible.  Make sure you have a GOOD ground.  don't wrap a wire around a seat bolt.  You shouldn't need a cap.

Also, very important.  Run the RCA cables on the opposite side of the car from the power, remote, and ground wires.

Have fun.

If I were to skip the distribution block, would it be difficult to add one later on if I wanted to add another amp?  Also, the xtant 403a amp is not internally fused and they require a 60amp fuse installed in line w/the power wire at the battery.  I can handle that, but the manufacturer states that for safety, an outboard 60 amp fuse may be added close to the amp.  Would that outboard amp fuse wire up just like the in-line fuse? and what purpose would it serve if an inline fuse of the same value is already installed?

as far as running the rca(s), can it/they go along side the speaker wires?  I have read numerous postings of running power down one side, speaker wires down the other side, and rca(s) down the middle.  I want to pull up as little carpet as possible as the wife is already nervous about me doing any work on it ('05 Scion xb) as it is only 3weeks old.  Will speaker wires and rcas cause a problem if they are next to each other?  By the way, thanks to everyone for responding/answering my ?'s.  I might actually get this all installed without catching the car or myself on fire.

Input wires such as RCA's or other twisted feed wires can run along with the output speaker wires.  Keep all power wires to the other side, incl. remote turn-on.  Distros and caps are the easiest add-ons to a system.  They each are mounted near the amp and the power wire is already there.  So there is no tearing up the car again.