I Have audi TT TQ 225 cabrio, with Bose Sound system & Audi NAVI & Audi Car kit, also i have Concert I (Radio Casette Tape) and audi 6disk changer

i Have replace front and read speakers with better.

can i replace bose amplifier with other???
someone have wiring of bose amplifier????

PS. I dont whant loose NAVI & car Kit.