In terms of performance, I have no reliable data on cross-firing 250 cards. Personally, I think its a bad idea considering the low-end processing power of r7 250 card. I would say only put up with the issue with crossfire if you can definitely get "more bang for buck" which is difficult to determine in this case. I always say that crossfire comes into play after $200 at least, or the issues with it, will not be worth the minimal gain.