are you still using the piece of crap 2v hu?UPDATE:
So i ended up buying another vehicle (not because of this problem lol) and I started off with a different, known working good deck. and a brand new amp wire kit. Bare metal, big seat bolt for a ground point.
Subs are a wee bit louder but no where near like they should be/used to be. Everything still checks out ok... im stumped lol. Maybe im cursed.
So far here is what I have checked/replaced
-Power wire and fuse holder
-Metal on metal contact bolted to chassis grounding point
-RCA's are brand new
-Replaced MTX 600w amp with Alpine 1000w amp
-Tried 2 sets of woofers (two 12" MTX thunder and two older 15" Lighting audio) Both sealed, independent chambers
-I have tried 3 different Head units ranging from 2.0v to 8v pre out
-Voice coil impedance checks out ok
-Alternator (running) voltage is just under 14.0v
-power wires, gorund wires resistance check is OK