If you want to stick with the hardware route, you may want to invest into a Dual-PCI motherboard specifically for this scenario. In my previous setup I had a GTX970 and an older GT640. Switching between GPUs will require you to reboot, go into BIOS and select a primary.
I've since dumped the 640 in favor of the built-in HD4400 in my i7 4770K. Check your CPU which may have an integrated GPU, it will be even a better representation of a low-end GPU than a dedicated GPU like the 650.