You would indeed benefit from an additional GPU, but I don't think is worth it for an entry card like the 260x, you would benefit way more from a single GPU, it should also be more power wise.
You should put your actual GPU on sale, you would get a good price, while its a recent card. Depending on your budget, you could get something much more powerful.
I wouldn't recommend SLI or crossfire with GPUs worth less than 300$, even there...
Cheers