A skillful player can "coax" some good sounds out of a mediocre instrument, but will sound even better given a quality instrument. On the other hand, a not-so-good player will fail to take advantage of *any* instrument's potential -- but will still probably sound a bit better using a fine instrument than a hunk of plywood.

The original question is still open, though -- do non-players take note of an instrument's namplate? One insight that popped up here was something I hadn't previously considered: musicians who play some instrument *other* than the guitar may not be any more likely than non-musicians to observe, or much care about, the brand name on the performer's headstock.