Well I would love to hit about 1,000 USD per month roughly as sort of my "magic" number. So at the current prices for GRC I would need ~425 GRC/day. I think once I get my 3rd GTX 1080 up and running, I should be getting pretty close. If I can't get it with my current two machines, I'm pretty sure upgrading to ThreadRipper this fall should get me there, but we'll see :-)