old stereo and speaker wire

Unless you are working with very fine equipment, just use good wire and bare wire on the ends. Some cable manufacturers even recommend bare wire because with soldered terminations, you introduce just another way to interfere with the signal.

If you have any soldering skills you could mate a short piece of 12 gauge Romex into a bundle of better grade speaker wire such as Monster cable or the RCA brand sold at hardware stores.

This would allow for larger wire and still fit the existing connectors.

Price would be very low and yet provide better performance than 18 gauge lamp cord.

Zip cord was what we used to use in those days, but you might try a set of shortened "pin" connectors. I used those on an old Marantz receiver and they worked just fine. Happy listening.