i have the full body zagg and it does protect my G1 real well. but it made it look ugly too lol. i used zagg because i put my G1 with my keys.
but if you're only using it for the screen, go for it. its really good.
hows your voltage? it might be your voltage or it might also be your box. you should do more than those numbers! or maybe your peak is lower but you burped a higher note?
just stick with your amp if will only run the sundown @ 2ohms...
but if you plan to change subs later on, then go for it.
i have first hand experience with a 3000d refurb from db-r and they are really good amps, my customer is still using it till this day.