Grassy weeds not responding to weed killer

I have about a 300 square foot area of my lawn, and a handful of other much smaller areas, where there are grassy weeds that are not controlled by Ortho Weed B Gon. I don't know if it is quackgrass or nimblewill or something different, but it isn't working.

I am planning an overseeding in the fall anyway, so is my best bet to spray those areas with glyphosate now, let it all die, and simply reseed those areas in conjunction with my overseeding in the fall?

I am hestitant to try Tenacity because of the cost, repeat applications required, and the fact that I am planning an overseed and will be watering the yard in the fall anyway. Might as well kill everything in that area and start fresh.

Pros/cons????