GTX670 video editing hinderance with dual monitors

I just built a mac with i7 9730K, GTX670 (2GB), 32GB DDR3, SSD for OS, RAID0 for storage.

I have a dell U2711 and need a dual monitor setup. This is a video editing rig so I don't want to lose performance in CS6 or FCPX. I am concerned because in order for FCPX to run effectivly on my macbook pro retina (GT650M 1024MB, 2.6Ghz i7) I needed to dial down the resolutions of both my monitor and retina screen (apple should be ashamed of themselves for marketing this computer as a pro line, but that is neither here nor there).

Ideally I would like to get another 27" 2560x1440 monitor but only if it will not effect real time render performance at all.

Any and all advice would be greatly appreciated.

Thanks