It looks like I won't make runs more than 50-60 feet and 14 gauge would be fine, though of course I understand the "be safe and wire for 12 gauge" especially as it's going to be a lot of work... It's just that those extra costs keep adding up... I'll probably be driving 8 to 6 ohm speakers all around with a 125 W or 145 W/channel receiver. Roger Russel's table show 14 gauge to seem just good. Maybe run 12 gauge to the main L/C/R area but stay on 14 gauge for in ceiling speakers?
The other reason I am posting is this calculator for speaker wire that I found in one of the thousands of 12 vs 14 gauge threads here. The speaker wire calculator seems to indicate that even 16 or 18 gauge produce non perceptible changes in sound (based off a <1 dB is not an audible difference) for reasonably long lengths... Is it not conservative enough compared to Roger Russell's speaker wire tables?