Solid core XLR interconnect recommendation (up to 300$ for a used 8ft pair) ?

FWIW, the whole point of balanced line connections is to eliminate the artifact caused by the cable.

This has as more to do with what is driving the cable than the cable itself. As long as the cable is built correctly (twisted pair within a shield) and it is driven correctly, it will not have a sonic artifact, solid wire or no.