Actually, the 700D is new, isn't it? It might not even be supported yet. In which case, you're probably waitng for ACR 7.5 for CS6, if Adobe decides it's free.
Yes, it is very confusing. No question about that.
Always use the highest version that will work with your version of Photoshop. In your case (CS5.x) that is ACR 6.7.
It helps to remember that once a given camera model is supported in a given version of ACR, it will continue to be supported in all subsequent versions.
In addition to support for newer cameras, each new version of Camera Raw has unannounced, unheralded bug fixes and improvements. So just use the highest version that will work with your version of Photoshop, as stated above. In the case of your version of Photoshop that is ACR 6.7.
But, your camera may not be supported at all yet, and you'll have to convert your Canon raw files to raw DNG files with the free DNG Converter once said converter supports your camera.
Message was edited by: station_two
Please note that I've edited my previous post to expand it and clarify it. Edits are not broadcast through emails, so you need to log in and access the forum through a web browser to see them.