986 with PCM 1 8-bit - what are my upgrade options?

[JonniH14]

I have a 2001 986 Boxster with a PCM 1 with Sat Nav 8 bit version and phone module with separate single Navigation CD drive in separate unit below. What are my options to upgrade? I would really appreciate any advice or answers to any (even one) of my questions below:

Can I upgrade to a PCM 2 or PCM 2.1 unit?
If yes, what do I need to know about my configuration to make sure I get a compatible unit? (Assuming I get a previously used unit).
I have read on other threads that whether I have Bose or Not is important. Is this just a case of seeing if I have Bose speakers?
I got the version of my PCM from holding in the bottom right button while on the AC screen. Are there any other hidden screens that tell me any more configuration/version info?
Can I use the CD Navigation drive to play music CDs?

Thanks in advance.