Mac Pro 2006 1.1 running El Capitan - GPU options expanded?

Hi Y'all,

Well got me old 2006 mac pro 1.1 running El Capitan 10.11.1

I have a Flashed ATI Radeon HD 5870 1024 MB running fine.

Info is a bit thin on the ground but wondering if a GTX card* would now work, say a:

Gigabyte Nvidia Gtx 960 Gaming PCI-E Graphics Card

Presumably after installing new drivers? hmm wonder if it would fit!

I'm aware that there may be a...

Mac Pro 2006 1.1 running El Capitan - GPU options expanded?