Please, do not buy Filemaker Server 13
A new Filemaker Server 13 . . . I can't recommended it to no one. I bought new version couple of months ago and after that my server has been up and running only couple of hours.
For most of us it is a big disappointment that FMS 13 needs dedicated server and cannot run machines where is OS X Server app installed. Of course, support documents tells you that it is possible but it isn't.
Lack of support is also very big issue. There is no decent manuals or support documents available. FMS 13 wants to be fully automatic and easy but when problems occurs there is not much user can do to solve problems.
Seriously guys, don't buy this stuff. It sucks.