Replacing Bose in '91, need help with components...

[harleyclassic]

I'm going to replace the Bose Gold system in my '91 vert and need suggestions on components necessary for a good sound system. In addition to the HU, I was going to replace the rear Bose speakers with 6 x 9s and 6.5s up front in the kick panels. What about an Amp or Subs? How do you determine what to use? I have to admit I have limited experience with anything more powerful than a basic deck but would like to take this installation a little further. I will be starting with a standard deck now but replacing with a Pioneer AVIC-N1 this winter. Thanks in advance for any info.