Yes, R9 300s and R7 300s still work well, but I'd suggest going with the newer RX series or waiting for Vega. It'll be making you profit longer.
The R9 390s crap all over the RX series cards depending on the coin but use quite a bit more power. I am getting about 270 sol out of an RX470 and 330 out of my R9 390x mining zcash. Ethereum the difference is not as much. The 390 gets about 3 mh over the 470. (these are all with stock BIOS numbers btw, there are plenty of tweaks you can do to up it on both cards)
Precisely the reason why I suggest RX series cards. Unless you get a real nice deal for the R9s you'll get more lifetime out of the RXs with their lower power consumption. Hopefully Vega will bring about an even greater hashrate boost without more power.