Actually, the fan is on the bottom of the PSU.
Since your case probably has the PSU on the top you won't have the fan blocked off by the case.
If you had a PSU with a top mounted fan you'd just flip the PSU over anyway.
It's possible you might want to add another case fan, or get a more powerful case fan replacement, if you find your system running hotter than you like. But thats going to be due mostly to the new, hotter video card. Just monitor the CPU and GPU temps and they'll let you know if you need to do anything more with case ventilation.