Tryid it on 280x
Got 12-13mh per one(8.1x64, cm9.
...nothing change from 15.12 driver. Stupid amd didn't applied their fix to truly good cards 
Got 12-13mh per one(8.1x64, cm9.
...nothing change from 15.12 driver. Stupid amd didn't applied their fix to truly good cards It didn't change because the R9 280x didn't suffer from the issue that the driver was intended to fix.
The 280x was never a "truely good" ETH card in the first place - that was the 290 and to a lesser degree the 290x.
Tahiti is arguably the best performance/price ratio for FP64 anyone ever released, but ETH doesn't use floating point....
The 7970/280x was actually very good at ETH only at the beginning. With DaggerCoins at Epoch #0 or #1 or so it can get like 28MH/s. And a year ago you could of found them on Craigslist for $100 second hand. The R9 290 while it was a little faster was always expensive to buy because it had high demand for gamers and was hard to find for less than $200. So the 280x was a better choice if it wasn't for the DAG bug.
R9 290 wasn't hard to find at under $200 a year ago - MUCH under, yes, mine were $179 from NewEgg when I bought them last spring (Sapphire reference design, I think they were factory refurb cards).
It's going to be an academic point in a few months though since the R9 280x is a 3GB card (I don't think anyone made them with a different memory capacity, but I MIGHT have missed a model somewhere).
I don't remember ever seeing a R9 280x for $100 or less on craigslist, but I do remember seeing some in the $120-$140 range so I wouldn't be shocked if they were less in other locations at times - especially in or near large cities with more competition and more supply of used parts for sale.
Maybe in your area you had better luck but I also got them refurbished from NewEgg last year and it was the best deal out of anything I found on Craigslist. On Craigslist alone it was at least >$200 and they were rare and hard to come by. I think since they were flagship models they were made in smaller quantities than the Tahiti.
The Tahiti were flooded on Craigslist, probably due to Litecoin mining days as I found that almost 50% of the ones I bought off Craigslist were mined at some point in their life.
