Have you considdered the R7 265 or the R9 270 in you're budget?
The R9 270 is probably one of the best value cards about at the moment- it's exactly the same GPU as in the 270X just clocked a little slower (and with a touch of over clocking can be just as fast or faster for free).
The R7 265 is a re brand of the old 7850 and is also very good value. Imo the 270X isn't worth the extra money over these 2.