A mining rig with 8 of these cards, riserless board would be great with 0.72 Ghs speed of mining in a single board. It is a lot better than E3 Antminer and it can also mine other coins, it should also shine on cryptonight algorithm. It is expensive to build such rig right now wih profitability down but for any believer in crypto it is wise to build such rig.
Dude, you mined any cryptonight coin recently? They are asic-ed to fook.
Even if these 7s double the CN hashrate of the 64 and power use stays the same (neither of which seems likely), you'd still only be breaking even on electric costs.