In my opinion a used GTX670 for 250$ isn't an awesome deal, even if not horrible either. How much does R9 280X go for in your parts? R9 280X offers probably the best price-power ratio of video cards at the moment, so it's a good reference point. In any case, keep in mind that GTX670 is hardly any beast anymore, so think carefully if you wouldn't rather add a little more money to the sum and get a modern card instead, so that it will still be jolly good when you upgrade the CPU, mobo, and memory later.