Second small GPU for more monitors?

[DatScrubBoi]

I have a GTX 1080 and I I'm using 4 of it's video outputs, which seems to be the maximum that most graphics cards support. I'm using the HDMI for my vive, and the 3 displayports for my 3 monitors.

 

I'd like to duplicate the feed of my center monitor and send it to a capture card over HDMI. I can't seem to find a displayport splitter that doesn't act like 2 separate displays instead of just mirroring the input (and I can only use 4 display outs) and I'm also worried about that introducing a little lag or not being able to support 144hz to my monitor.

 

If I was to buy a low-end GPU like a GT 1030 or a GTX 750, could I pop that in and use it to mirror my center screen in Windows display settings and not cause much of a hit to my performance?

[Nocte]

Technically you should, albeit not with fullscreen applications (iirc).

If you have an iGPU you could try using that?

[DatScrubBoi]

CPU is a 9600K. Yeah I thought about using the iGPU but I know that results with that can be a little hit-and-miss sometimes and I'm not sure what kind of hit my CPU would take for that, I do love my multitasking and it's already hard enough to even watch a video when Hammer is compiling a CS map and pegging my CPU, so I was hoping a dedicated card might help with that a little.

I'm open to whatever suggestions. Thanks for any help