Don,

Yeah, there's probably no easy way to quantify unique listeners and listens. I do think it's around a couple hundred though, just being part of a few completely different online communities with almost no 'Venn Diagram' overlap between them, and having actual ways to count unique listeners at a couple of them, it turns out to be about that number.

Quite shy of the '1000 true fans' legend on the internet that states something to the effect that 1000 true fans are what it takes to potentially make a living as a musician. (Google '1000 true fans' for more info)

But as I stated above, garnering that kind of a fan base takes some hard work and determination, and a willingness to accept defeat. Smells like work. Not sure I want to go there.