There is your Polaris 10. I know you said SLI (Its actually CrossFire), but this is a mainstream card. If the price point is 300$ USD, thats slightly less valuable than a GTX 1080 at 600$ USD. This is AMD's first time optimizing performance-per-watt. Remember its Mainstream class, not High End/Gamer class. That means AMD has some effecient GPU's coming later this year. GTX 1080 is over 400$ USD which makes it Enthusiast class. Don't expect these cards to be competing against each other, even 2xPolaris 10 in CrossFire vs 1 GTX 1080.
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