i got my 1070 second hand for around 270 during the crisis.
if you find one that's lightly used, go for 1070. Otherwise, AMD if you want more freesync compatibility for future (rx 480 or even 500 series) or 10606 gb model. 1050 ti if you really really need something for cheap.
or wait for the new 1660 ti which is going to kick butt.