http://www.ebay.com/itm/25-feet-18-AWG-Silver-Plated-PTFE-Wire-Gray-Solid-1-Strand/380927049734?_trk...
and some connectors from Amazon...
https://smile.amazon.com/gp/product/B01IBFNQP6/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
and got it all hooked up in a few hours. Those solderless connectors relieved my worries about trying to get a good joint on little barrel plugs.
I played my regular test piece (an upsampled-to-DSD recording of Vince Guaraldi playing "A Flower is a Lovesome Thing") and have to say I hear improvement in the sound quality: greater definition, sense of presence. Guaraldi’s recordings are often made on a sort of de-tuned piano with a slightly honky-tonk ring on each note, and for the first time I could understand why he must’ve liked that sound.
Thanks again for all the suggestions. This whole upgrade cost me about $35 and was well worth it.