Asus should be able to tell you a good way to ship back. If you have any electrostatic bags from any electronics. Put the card in that first before wrapping it in bubble wrap or paper. I would suggest you keep you gpu boxes in the future. For this reason alone. I resell my GPU's sometimes and keeping the boxes is a big plus there too.
Just saw you said it is over 3 years. It may be out of warranty but asking sure can't hurt! Before writing that card off, make sure to try it in another machine. If you don't have another maybe a friend can help you out. Then you will know for sure if it is your card. It can always be other components that are a problem like memory, motherboard and more often a power supply. Even a corrupt windows installation can be the culprit.
If you are building the new high-end system yourself, I have a suggestion. Buy the PSU now and test that in your current system. If you are buying a custom built system that won't be an option.
One other thought comes to mind. Just for testing purposed, could you try a different PCI slot? I know you may get as may lanes. But it will give you another piece of information to factor into a resolution.
I think Ive solved my problem, I removed my GPU so I could get the code on it to submit an ASUS support ticket. I was inspecting the card while it was out of my system and somehow between the back-plate and PCB i notice a dust bunny caught between the two contacts of a capacitor. Ive cleared it out and inspected the card for anymore but it looks promising now. Im going to game a bit more just to check that it doesnt crash any more but Im hopeful that this has fixed the issue.
After more testing, it appears that, that wasnt the problem, it was my cablemod vertical pcie extender that i probably shouldve mentions for troubleshooting reasons.
This is a bummer considering i had to modify my case and the extender so everything could fit nicely
(1 slot taken out of the vertical mount as well as a hole in the bottom of the case so the GPU had clearance from my large CPU cooler)