I could but I like to have excess wire for when I connect the 4ch amp. Right now I am just gunna wire the mono and subs.

To break it down, I will have 2 amps 800W TOTAL RMS
Both amps combined max amperage is 120A (40 and 80 fuse)

I want to know if it will be OK to run 4 AWG power wire to d-block outputting 2x 8 AWG to both amps. Doing the calcuations this is JUST pushing the limit of amps per cable length/gauge. Obviously, it would be best to use 1/0 from battery to d-block and 2x 4 AWG but can I get away with 4 AWG > 8 AWG?

Thanks.