adding A second Nvidia card to Aurora r6

Hi,  I have an Aurora R6 equipped with a GTX 1080 (8GB). I primarily use the rig for running machine learning experiments using Tensorflow on Windows 10. Lately I've been running out of VRAM on the Nvida card as my experiments use more and more data. Apparently some of the VRAM is reserved by Windows 10 display driver,  leaving only 6.6 GB available on the card (see Windows 10 does not let CUDA applications to use all VRAM on graphics - Microsoft Community ) 

I am considering adding a second Nvidia card to distribute the memory resources across two Nvidia cards. I have a couple of questions on what card to get to run in parallel with the pre-installed card:

1- Can I add a second card of the higher specced GTX 1080 Ti 11GB or should I stick with the same model (a plain GTX 1080)?

2- In case it is recommended I add a card of the same model based on the Nvidia GTX 1080 8GB, does it matter which brand name I go for (MSI, EGA, etc.)? 

Thanks