ViperGuyMike, I'm the original ViperGuy here. lol 
I had this screen name 3 or 4 years ago, then lost it, but just reinstated it, although I lost my street cred and status somehow. I also sold both my Vipers so I'm Viperless. 
But I have a Demon on the way!
A couple months ago 1070Ti's would have been the way to go at $550, but at today's prices of $700+ (to get them in bulk, not piecemeal) it's not worth it. Neither are 1080Ti's at $1000. At $900 1080Ti's seam like an ok deal compared to what's left. RX570's and 580's at $380 are not bad, but if the rumors about an ASIC ETHASH are true, then all AMDs would have to go to Equihash where they don't do so well. The other problem is the lower grade you go with the card, the more of them you need, the more MB's, Ram, and PSU's you need. Each rig takes up a standing power cost as well. Two rigs use more overall energy than one rig with the equivalent GPU hashrate, and cost more. There's really not a "Great" card to buy right now, that's readily available. Yes, you can piecemeal something together one-by-one, but if you need a complete matched rig, the options are low. If it were me, I'd try to get 1080Ti's for around $900 or less. They will hold their value better in the long run, and you'll have less of them to sell off later.
I had this screen name 3 or 4 years ago, then lost it, but just reinstated it, although I lost my street cred and status somehow. I also sold both my Vipers so I'm Viperless. But I have a Demon on the way!A couple months ago 1070Ti's would have been the way to go at $550, but at today's prices of $700+ (to get them in bulk, not piecemeal) it's not worth it. Neither are 1080Ti's at $1000. At $900 1080Ti's seam like an ok deal compared to what's left. RX570's and 580's at $380 are not bad, but if the rumors about an ASIC ETHASH are true, then all AMDs would have to go to Equihash where they don't do so well. The other problem is the lower grade you go with the card, the more of them you need, the more MB's, Ram, and PSU's you need. Each rig takes up a standing power cost as well. Two rigs use more overall energy than one rig with the equivalent GPU hashrate, and cost more. There's really not a "Great" card to buy right now, that's readily available. Yes, you can piecemeal something together one-by-one, but if you need a complete matched rig, the options are low. If it were me, I'd try to get 1080Ti's for around $900 or less. They will hold their value better in the long run, and you'll have less of them to sell off later.