Mining cryptocurrencies can turn out to be an interesting venture with good GPU and ASICs to mine with.
Most cryptocurrencies can be mined with GPU power but Bitcoin requires ASIC miners that are developed with Bitcoin mining in mind, and which offer much better hash rates for Bitcoin mining than does any GPU. For instance, a single ASIC miner that goes for about $200 works much better than high-end GPU such as NVIDIA GTX 1080TI that cost three times more.
Mining GPUs are selected based on budget and mining efficiency. You need to also look at the power efficiency against returns to see if you will get any profits at the end of the day.
Some of the best GPUs with which to mine cryptocurrency include AMD Radeon 295×2, Sapphire Radeon AMD RX480 / RX580, XFX R9 390X and NVIDIA GTX 1070, Sapphire Radeon RX 470, Radeon HD 7990. Some of these might need tweaks to achieve the optimal hashrate or power consumption threshold desired by the user.
AMD Radeon R9 295X2
Radeon R9 295x2 Dual-GPU card was manufactured in 2014 and features 2 physical GPUs on one single board. It manages a hash rate of 55-60 MH/s, which is the best in the market so far, and costs about $500 on eBay. Each of the cards will draw 500W of power, so including 7 into a single system will see you using 3,500+ Watts.
Therefore, it would only be a great option if you have access to cheaper electricity.
In terms of profitability, you can get around $2,000 a year using a a single AMD Radeon 295×2, minus the cost of power, so it is not a bad investment if the price of electricity in your area is low.
This GPU is, however, hard to come by since production has been continued. You can get a used one.
AMD RX480 / RX580
RX480 and RX580 GPUs manage a hash rate of between 22-29 MH/s, depending on model and settings, and thus are great for mining Ether. They are best value GPUs because they are quite power efficient if tweaked. You can adjust them to the tune of 150W TDP with the same high performance.
The excellent price-to-performance ratio (they were retailing at around $200) caused these GPUs to sell out in a blink of an eye so they can be a bit expensive if you get them at Amazon and eBay.
XFX R9 390X
XFX R9 390X GPU costs a little bit more than the RX480s and RX580s and manages a higher hash rate of 30 MH/s. It is a predecessor of the RX480 but, although it uses an older architecture, the 512-bit memory interface allows it to perform better.
Although it offers about half hash rate than 295×2, it uses about half amount of power compared to 295×2.
It has been discontinued but you can still get a few units out there or buy used ones.
NVIDIA GTX 1070
GTX 1070 is the most available option out there for GPU miners. It manages a hash rate of about 31 MH/s if properly optimized. It is more power efficient compared to the rest of the options, requiring 180W to run at full power
Mining graphics cards
NVIDIA recently announced and so did AMD that they will be releasing mining-optimized cards. This will likely make mining a bit less expensive. These are redesigned cards based on existing architectures such as Polaris, for AMD, and Pascal, for NVIDIA. They will come with no video ports for some models (which cuts down costs), optimized fans for 24/7 operation and lack any bling.
The NVIDIA P106 is used by the GTX 1060 lineup) and together with the Polaris 460, 470D and 560D, are some of the great graphics cards for miners out there.