Im not familiar with the 3 shops on the Cape perhaps others can comment. But if you can get into Boston for a day trip Stereo Jacks is always a fave 10 minute walk from Hvd Sq Nice dollar bins if you like to dig, Newbury Comics stores always has something, I prefer the Newbury St location, Looney Tunes in Allston now if you like to dig just call for hours. If you are genre specific I have others recs