97 wrangler redoing system melted power lead

Helping a friend with repairing his system 97 wrangler 4L 6cyl 5 SPD JVC CD player with USB and 3.5mm input Amps JL g4500 Kicker monoblock 500.1 zx/ series or kx I thjnk Stereo speakers 4 After markert coax Sub Sound stream t4 12in dvc 1ohm stable My buddy melted his power wires from the battery to the amps Due to what I'll guess is using too small and cheap powerwire (10 gauge) when he needed to running quality 4awg Since the power wires were melted all the way from battery to the amps should the grounds and remote turn on wires be replaced also And do the amps need to have a volt meter check the input and out puts is there any visual inspection needed on the amps boards etc ? Before it has juice put to it? Also He had the dvc sub wired in parallel to the monoblock , which would of been running that kicker mono amp way below its approved ohm load srability which I'm sure didn't help He bought quality 4awg and a new inline maxi blade fuse holder A distribution block 4awg-8awg I'm trying to help him reinstall its done correctly etc. As I don't know who did it originally Will a quality 8 gauge wire be suffcient? Or is 4 gauge a must for the power leads off the distribution block And What should the nax length of the power wires be.? That come off the distribution block to the 2,amps For grounding is 4 gauge necessary or is 8gauge sufficient I know they need to be less than a foot long Grounding should not be to floor board correct? Where is a good alternative grounding point Since its in a wrangler and he likes having the top removed,offroading etc. I was going to put 1/2 inch spacers between the amp and floorboard, to help minimize the amps direct contact with liquid on the floor board considered mounting them upside down and also using the spacers between the bottom of the amp and seat The sub enclosure is also being redone due to water exposure it calls for a 2.2 cu ft ported which he I think had behind or under the back seat I'm also shrink tubing all convections and then wrapping them in high grade electrical tape for weather proofing Thanks

DO not mount the amps upside down! Do read the what is a proper ground sticky and the Big 3 sticky.Top Secret, I can tell you but then my wife will kill me.