As I mentioned in another thread, I don't have a CD changer, so I can't fully comment on their capability, but given ****** FM radio audio, I like my Powerbass speakers. I run their 5.25" component set in the front doors and their 5.25" coaxial set on the rear deck and have a MACH RCU.
I don't know about a G3 install, but my G4 was a piece of cake.
Front: Unscrew all of the visible screws in the door panel, pop the panel loose from the door by starting at the bottom, lift up and off the door lock rod, disconnect the power window and door lock switch, then set the panel to the side. Since I was installing components, with crossovers, I removed some of the sound deadening padding in the upper left hand corner of the door panel (Towards the rear doors), as well as snipped off some plastic "casting flash" that was in the way. Using 3M super strength double-sided tape (The same used on Ventshades) I mounted the crossovers there. After some quick wiring and mounting the Scosche 5x7/6x8 adapter in place of the factory speaker, I was done. I did both front doors in about an hour's time, not bad for not knowing what I was getting into.
Rear: Couldn't be easier, push down, out and up on the bottom seat cushion. Then the cushion is removed from the car. Slip two screwdrivers underneath the 3rd brake light, it pops up, pull up and out and disconnect it. Two bolts hold the back of the seat, then lift that up and out, make sure both rear doors are open when you do this. I just flipped mine down and sat on the back of it while working on the rear speakers. Mitchell-On-Demand says to remove the trim near the headliner, but I left mine in place without issues. Pop up the two plastic body panel retainers holding the carpeted section, then remove that section. Quick wiring and mounting the speaker adapters and done. Rears took me less than 30 minutes.