It's been a while since I last talked about cryptocurrency mining. The past two years have seen plenty of changes if you drill down, but pull back and look at the big picture and the cryptocurrency world hasn't radically altered our finances. Scamcoins and hacks have come and gone, Bitcoin continues plugging along, but Litecoin has dropped to under $4, Darkcoin has changed its name to Dash, and the second most popular cryptocurrency is now Ethereum.
I'm not going to get into the discussion of whether or not Ethereum is a better or worse solution than Bitcoin -- or any number of other coins -- but the fact that it's actually supported on Coinbase says a lot about it's potential. It's currently trading at over $13 as well, which is pretty impressive. So let's talk mining potential.
First, if you hopped on the Ethereum boat at launch and saved your coins, congratulations! You've struck it rich and should be quite happy. For us Johnny-come-lately miners, it's going to take a bit of work to break even. I've poked around at looking at Ethereum mining (including dual mining with Ethereum and Library Coin). You've got a few options, and here's what I've found in terms of hashrates, using the Claymore Dual Miner 0.7.1:
RX 470 (stock): ~20MH/s ETH, ~25MH/s LBRY, 150W
RX 470 (OC): ~25MH/s ETH, ~32MH/s LBRY, 180W
RX 480 (stock): ~24MH/s ETH, ~32MH/s LBRY, 150W
RX 480 (OC): ~28MH/s ETH, ~36MH/s LBRY, 180W
R9 390 (stock): ~26MH/s ETH, ~37MH/s LBRY, 275W
R9 390X (stock): ~28MH/s ETH, ~40MH/s LBRY, 275W
R9 Nano (stock): ~26MH/s ETH, ~37MH/s LBRY, 175W
R9 Fury (stock): ~28MH/s ETH, ~40MH/s LBRY, 275W
R9 Fury X (stock): ~30MH/s ETH, ~42MH/s LBRY, 275W
If you look at hash rates, power requirements, and perhaps most importantly, price, it should be pretty obvious why the RX 470 and RX 480 are your best bet. Overclocking will give the RX 470 performance relatively close to the RX 480 (overclocked as well), and power requirements and price are substantially lower. At $200 per card, it's possible to build a complete mining rig with four RX 470 cards for around $1350.
Now, a few notes about the above. First, most of the systems are running AMD's latest Crimson drivers, on Windows 10 -- not the ideal scenario apparently, as Crimson 15.12 is recommended. I don't know how much 15.12 drivers would improve things, though with RX 400 cards you need more recent drivers regardless. Anyway, running Windows 7 appears to improve performance by perhaps 10 percent, so keep that in mind.
Here's the thing you need to ask: How much money can you make per day with such a system? Or in other words, how quickly with the PC pay for itself? The cryptocurrency market is always a bit volatile and difficult to predict, but with services like Nicehash, you can at least eliminate some of the system management time and generally get a decent return. Best guess, you'll make a net income of around $7.50 per day after power costs with the above mining PC.
Bottom line, then: 180 days of mining to break even.
And if you're wondering, Nvidia mining with GTX 1060 cards is also possible, and the time to break even really isn't any worse than the AMD cards. You'll consume less power and likely have to mine different coins (I'd recommend just going with Nicehash and letting it manage switching), so you could drop down to an 850W Platinum power supply and still be safe.