Yeah, checking EVGA's B-Stock on the Titan X cards is a good thing to do. I've seen them there for $700. They come with a warranty and is a direct purchase from EVGA, so it's pretty reputable. Plus, they don't have the Titan X cards on B-stock that often. So if you get one and it doesn't work, there's a good chance they'll have to replace it with an A-stock (i.e. regular retail) card. Either way, it's a good way to go for good deals on the best cards if you stroke at the right time.
I generally agree with the used thing, unless you buy from a seller that won't give issues on returns and replacements - hard to find in the used market but possible.
Also, yes, shoutout to scrapyard wars and LinusTechTips generally. Good stuff!