I'm running a little bit of everything. Factory amp to an Audio Control Line output converter, to a Rockford Fosgate Processor, to JL Amps, to Hertz component speakers and a JL sub. With a little bit of sound treatment in the doors and back wall, I'm running quite loud and clean, with little to no distortion.
Was at a car show a week or two ago and there was a kid that had 4 or so 12's crammed into the trunk of a little P.O.S. Hatchback. (Bought rattled the damn thing to pieces) Sounded like shit compared to my single 13.5 JL shallow mount. (Thanks Noah!!!)
Started down pouring rain at one point, so I fired up Thunderstruck and cranked it up to max as everyone ran for cover. Even with the windows up I'm pretty sure everyone could easily here it, based on all the looks I was getting from across the street. Hahaha
Anyway, the main point for upgrading to modern equipment is more power, much higher efficiency, and lower cost (maybe, depending on the route you go). The main thing is really the efficiency. I can run 1600 watts of total audio at max volume while also running a 30" and 40" LED bar, Two 90watt LED hood Lights, six Whelen Micro Pioneer LEDs, two flush mount bumper LEDs, and the HIDS on bright. All that and nothing even comes close to dimming on the bass hits. That's what you really like to see!