Ecky :
I believe you can get a PCIe card that has an M.2 slot, but you probably won't be able to boot from it without BIOS support. I assume you want to boot from it.
Thanks for the reply Ecky.
I was hoping to boot from it
System is i7 6 core | GA -X58A-UD5 MB | Dual GV-R685oc-1GD GPU | 24 GB Ram
Bit of a power hungry beast by modern standards. With the M.2 and a new 1070 GPU I could get a few more years out of it.