Hey,
From what I can see it looks like a nice case and that’s a reasonable price. My guess is the fan slot you can’t see is the one behind the motherboard to help keep the cpu cool. A unique feature but probably wouldn’t be necessary in your build. As far as fans go I’d recommend getting two fans for the front to pull air into the case and that should do nicely along with the preinstalled fans.
For the new gfx card I’d push your budget to $300 and grab a 660 ti if you want to stick with nvidia.
Hope that helps.