i run a preamp eq, and always have..This one here is 12v rms,and has an aux output, which im sure you can find an aux-usb adapter pretty reasonable.Much better to make adjustments at your finger tips, and fine tune rather than pushing a button, and going through a bunch of BS just to tune a song in,.Id run This
buy a new head unit with the aux/usb be the best thing to do then,and add the preamp if youd like the upper voltage ,and adjustments at your fingertips,about all i can tell you.Good luck, hope you find what you need
I had a crossfire one back in the day and loved it. Payed around $150 for it in the late 90s. Just didn't want to get some junk. How is the sound quality on the earthquake? Got eclipse amp running old school Boston pro componants 6.4s and Rockford 6x8 componants in rear doors. I got a I phone and pod, just a USB with a storage drive thing would b easier