Attenuation/Power issue with JL Amps

I'm having a heck of a time with an install I recently dropped in my POS 93 Toyota Corolla.  This thing is the base model without any options except air conditioning.  I have an Optima RedTop, grounded with 2-gauge, running 2-gauge power wire to the trunk.  I also have a length of 4 gauge running directly off my alternator to my battery.  (before I ran this wire, the system would kill the battery even while driving around.  I'd park and the car wouldn't start.)

I had a JL Audio e6450 and a 500/1 running in my car before.  Not quite running to potential; the 500/1 would cut out on huge base drops and higher volumes, but I never got around to screwing with it because it would be volume I couldn't take in the car anyway.  I never had any problems with 6450 cutting out, ever.  Anyway, I had that running off a Pioneer 7400 MP which had 2x2volt preamps. 

So the system gets stolen last month and insurance check in hand I picked up very simalar stuff; a JL Audio e6450 to run my highs and the new e1800D to push a 13w6.  I purchased an Alpine CDA-9833 with 3x4volt preamps (they stole my face plate, but not the deck itself, go figure) to run this stuff.  So the sub wouldn't even play at an audible volume.  The amp would turn on and the woofer was moving if you felt it but not audibly.  I'm talking like the first few notches of volume.  So I disconnected the sub amp and tried to run the e6450 by itself . . . simelar problem.  I could get a bit of volume... a loud speaking voice perhaps, but then the amp would attenuate output like 30 decibels or so back down to near silence.  It sounds like its switching to a protection mode or something.  The weird part is it doesn't seem to matter much where i set my gains, as soon as I hit volume #20 on my deck (Alpine decks go from 0 - 35 on their volume control) the highs attenuate themselves.  If I turn the gains all the way up, they get right loud (but nothing close to acceptable performance) but still cut out at volume 20.  If I turn the gains all the way down, they just attenuate at real quiet volume #20.  At no point while attenuating the sound or otherwise running, does the amp's protection light turn on.

Which is why I keep mentioning my deck.  Could this thing somehow be the source of my plight?

I've had a few friends look at this and even called JL's tech department.  His exact phrase, as he heard the phenomenon over the phone a delighful "Man, that's W E I R D." 

So far, I've regrounded my amps, checked everything I installed this time.  I can't figure out the issue.  I keep coming back to the power supply, but I had that tested at Advance Auto and I'm pushing 13.8 volts at the battery.  I had the guy even test my positive and ground in the trunk and that was sitting on 13 volts as well. 

I have the 6450 wired a little funny, but, again, it worked great the first time:  Its a 6 channel amp, 1&2 are bridged @ 4 ohms/150 watts to my front right, 3&4 bridged to my front left, and 5&6 running stereo @ 4 ohms/45 watts to my rear coxials. 

At this point I'm half worried I'm going to blow the amp or something just listening to the talk radio I can squeeze out of the damn things.  Nevermind the fact I can't even come close to running a $1000 amp/sub combo. =/  I've been tinkering with this for weeks and now am seriously banging my head against the wall.  Anyone? Please?

did you actually try another HU?  either another of the exact same model or else another completely different HU?

Naww I don't have access to another head unit.  I got this one online so if its the problem it will probably be the hardest to fix. =/

Would that be my only recourse?

Tomos:

I actually fixed my problem . . . . it turned out . . . unsuprisingly, to be my head-unit. 

See, the amps still cut off, but at a volume that I know would be more power than I can get to them so I'm not so perplexed.   I need to get a larger alternator to run these amps . . . they huge.

I know when my 500/1 was cutting out, it was a voltage problem, never a problem with the amp.  I mean, I could get it right loud before that would happen and it would only do so on huge drops or prolonged playing.   Usually it would cut off for a moment, then cut back on for a moment, then kinda just cycle like that for awhile. The alternator I have in my is a real weakling and I'm looking about getting that worked out right now.

Is your amp cutting out or attenuating itself?  Are you running any other amplifiers along with it?  500 watt JL amps have reputatedly put out as much as 700 watts into reactive loads . . . that is alot of power for an un-upgraded electrical system.