GTX 660 vs GTX 950 Equal or Greater

I just did a RMA on my GTX 660, but they sent me a GTX 950 since they did not have GTX 660s. Their warranty policy states that the RMA will replace with equal or greater. So is GTX 950 considered as equal as GTX 660? or should I complain and ask for GTX 960? I guess the performance is about the same, but the fact that it's a lesser model bothers me.