Wanting to know if it is safe to use the Power lead under the back seat for a power supply to a amp??? AS long as I put a good size fuse between it and the amp???

depending on what size amp u r going to run. if u r lookin' @ runnin' some serious power for a big aftermarket system, u should always run at least a 4 gauge power wire directly from the battery, with a fuse within 18" of the batt terminal. make sure u use no less than (1) gauge smaller than your supply size 4 your ground wire. ie; if u run 4 gauge to supply power 2 the amp, u should use no smaller than a 8 gauge for the ground wire. remember 2 always keep the ground as short as possible.

In simple, NO! Get the power straight from the battery or from the power distribution block to the fuse block under the hood, or the jump starting psot.

Dido. If you're installing a heavy setup, then get the power from the battery directly. I installed 2 amps. 1to power my 2 12" Punch 1 subs & 1 amp to power the 5 3/4" speakers both from the power source underneath the rear seat & have had no problems whatsoever. My headlights don't even dim up when I turn it up. Just make sure you use adequate guage in power cables & fuses.