I went through this last year. I tried the Sigma 18-50mm f/2.8 DC DN Contemporary, but honestly, be careful with the lack of stabilization... it's a risk for ur shots!!

TL;DR - basically need to know if you care more about low light or having more zoom range for your travel stuff!! Just found this thread - congrats on the a6700!! I realy want that camera too but it's so expensive lol. Since your looking for a "one-and-done" and trying to stick to that $800 budget, I was wondering what you actualy shoot the most? Like, are you usually indoors or shooting at night where you'd need the better aperture, or are you more of a daytime traveler who needs the extra reach for stuff thats far away? Also, does it have to be brand new or are you open to used gear to get more bang for your buck???