you don't say if you're stateside or not... however, in the 150-200 range the best buys would be (ordered in pure gpu strength, not cost)
Low End - R7-260X < GTX 750ti < GTX 650ti BOOST = HD 7850 < R7-265 < GTX 660 = R9-270 < R9-270X - High End
Of course if you're in the states the chances that you'll find an r9-270 or r9-270x for less then $200 is pretty thin. In that case i'd say your best bet would be a GTX 660. Understand the 750ti is pretty close in ability to the 650ti Boost and hd 7850... but in benches it most certainly trails behind both cards a little bit. The r7-265 is just a factory overclocked version of the hd 7850 so it's not all that much faster, though you can find it for less then $200. The GTX 660 and r9-270 are pretty close to identical in performance... depending on overclocks and coolers, overall they're shockingly similar, so whichever one you can find for less would be a better deal. meanwhile the r9-270x is not going to be found for less then 200 unless you're really lucky.