One of the PDX 4.150 amps in the pic with the Doberman is currently in my car. Se7en is an awesome guy to do business with. His equipment is always very nice, and usually pretty rare. I would not hesitate for a second to do a $1000+ purchase from him.
I definitely prefer 'concert', even if I'm listening to 'night club' music. I'm pretty sure rear fill would completely fukc up the stage just in front of my windshield I've been working so hard to get.
I'm guessing your birthsheet is the small white one (half-sheet of paper)? Your amp probably does over 500 W.
PG told me that the x600.1 amps are actually around 40 W less at 1 Ohm as opposed to 4. should be inaudible unless there's other factors involved.
Does your Ranger have the premium sound system? You might have a loose connection/ground/something related to the factory amp.
Search up Ranger/Explorer forums for location of the factory amp. I think it's behind a panel on the passenger side somewhere. Factory deck wiring should lead you...
your lights may dim a little, but not much if at all. i wouldn't say it's "harder" to make power at 4 Ohms...i think it's harder on the amp to make power at lower impedance, because it requires more current.
I think the kicks would be better for a driver that performs better on-axis, plus it could eliminate door rattles, and allow you to fit a deeper driver than you could in your doors. If you do go with sealed kicks, try stuffing them with polyfill.