what was it going to be used for, most of the time it's gaming which I am assuming yours is for that. I tend not to be too biased on Nvidia and AMD as both are good providers. Nvidia tend to have better game support and drivers whilst AMD tend to have better prices on their GPU's. A ATI 7790 or a GTX 650 Ti would be my top pick for under $150 and are decent performers for the price, from those two I would go for the 7790 as it's performance edges it slightly and can be found for roughly the same price. Just need to make sure your PSU is at least 400- 450 watts so you have headroom for the cards in case of overclocking later and PSU efficiency.