Personally I would wait for the new ones, but if you cant, then technically speaking the R9 390 is easily more powerful than the GTX 970 for the majority of things.
buying a 970 now is just sheer stupid, just saying... in 2 months you have new nvidia cards, which will be, probably, not flawed. 970 will get cheaper etc...
Easy fix for coil whine issue (from reddit): "In order to fix coil whine (which is the inductors switching on and off at the same rate as your psu is supplying power to them for a quick and dirty explanation) overclock and overvolt your card a few mhz till the whine goes away."