I know 4x native works fine for every game I've tried when using a Radeon 6970, and gives me no slow downs. I check my GPU usage in MSI afterburder, and it never goes above 60% and normally hovers around 35%.
So any AMD GPU = to or better than a Radeon 6970 is more than enough for Dolphin. A Radeon 7850 is basically = to a 6970, and you can buy one of those for $180-$200.
For high end GPUs, don't go AMD right now, because the price on them is heavily inflated due to Bitcoin/Litecoin farmers driving up the demand. Because Nvidia cards suck for coin mining. So right now, Nvidia is definitely the best price to performance ratio on the higher end GPU models. For example, AMD has nothing in a similar price range to the 770, which would be the R9 280, which is more expensive than a 770, and not hardly any better for gaming. Same thing applies when comparing the R9 290 to a 780.
A Radeon 7970 ghz model is still a very good GPU if you can get one, and its basically = to a R9 280, and its also cheaper.
So any AMD GPU = to or better than a Radeon 6970 is more than enough for Dolphin. A Radeon 7850 is basically = to a 6970, and you can buy one of those for $180-$200.
For high end GPUs, don't go AMD right now, because the price on them is heavily inflated due to Bitcoin/Litecoin farmers driving up the demand. Because Nvidia cards suck for coin mining. So right now, Nvidia is definitely the best price to performance ratio on the higher end GPU models. For example, AMD has nothing in a similar price range to the 770, which would be the R9 280, which is more expensive than a 770, and not hardly any better for gaming. Same thing applies when comparing the R9 290 to a 780.
A Radeon 7970 ghz model is still a very good GPU if you can get one, and its basically = to a R9 280, and its also cheaper.