Help for a Lo-Fi guy

I have 2 Cary CAD-300-SEI integrated amps I am trying to help a friend of mine get some info on. Her husband passed away, and left these along with some other tube amps . I have done some research online and discovered that these are 15watt tube amps that are best used with efficient speakers , or possibly as headphone amps. I am trying to determine , desirability, possible used price etc. My experience in the audio world is very limited. I am using old Yamaha separates (M85 amp,C80 pre amp) that I`ve had for decades, so any help would be greatly appreciated.....Thx