If you don't have a problem with electricity and cooling issue, 295x2 is one of the best option.
It shows the best ethereum hashrate among ALL single graphics cards, consumes a lot of power.
Very cost effective if you are free from electricity bill.
Most folks that know what the R9 295x2 is don't count it as a single card - it's 2 GPUs on one card, and the DRIVERS see it as 2 GPUs when counting against the "number of GPU limits" of the drivers.
It DOES make for a nice compact rig though, *IF* you can keep the beast fed and cooled.