I have a 10-20, and I'm wondering if that 20-28 gap would be fairly big. I would also purchase an 85mm at the same time, and it would probably be the 1.8.

So either 10-20, 17-55, 85 1.8 or 10-20, 28-70, 85 1.8.

I'd get either one used at hopefully a little less than $1000 plus the 85 1.8.