I have a 2013 street glide with the older Hogtunes speakers and amp. Can I upgrade to the Biketronics BT7P1 7.1 speakers now? If so what about upgrading the head unit later, to say a Sony from Biketronics?

I forget how things work with the 2ohm and such.

 

Yes you can upgrade the speakers now, head unit and amp later if wanted. For folks who are going to do a setup in stages this is always the way I suggest you do it. Speakers first, then the rest later.