Opened up the left panel in the trunk and saw these two things. The one with the slats in the background I take it is the amp for the sound system?

What about the other one on the left, with the black wire that has the purple plug on it?
.
.

 

you are right about the amp.
don't know the other thing, but its not Bluetooth (as I don't have it on mine).
maybe satellite radio? or BMW assist?

 

I think you are correct and it's the Sat radio.

 

I do have Sat radio, so maybe you're right. I could unplug the purple connector and find out... :-)

I wasn't sure if it might have been the hard drive for the music collection (where is that?) or for the NAV, in case I have the HD system (I don't know if I have a HD or a DVD one), so any tips on where these two are located would be good too!

 

I think since your car is LCI its HD and that sits behind the centre console, i.e. behind and under the CD slot. But not 100% on that.