Boxes

I also keep all the original boxes even thought it's a pain to find space at times.  Last year I sold a pair of Marlin Logan speaker I'd had for 20 years.  The buyer was amazed and pleased that the speakers came packed in OEM boxes.  

Yes definitely, they are valuable. Shipping stuff like speakers gets really challenging without them. Many companies actually have new boxes for old equipment… I think Pass does. 
 

I tried selling some old ugly black ribbon speakers and the cost of constructing shipping crated was a couple hundred dollars. My speakers now have an incredible polished red violin wood finish… with out a single scuff or scratch. I cannot imagine transporting them without the original packaging. 

I don't know about potential buyers, but they certainly have value to you. You need them to ship the speakers.

i agree w @roxy54 

Yes!

I keep every box my equipment comes in, even the small stuff like cables. Especially since I tend to change stuff frequently.