As several people have said already, measure your case from the PCI bracket area and to the right 10.5 inches.
I have heard many people say that their GTX extends just to the edge of their mobo. As this is no general rule for all mobos I'd measure it out but I would say "most likely" the GTX will fit in most cases where there is at least a little room to the right of the mobo edge. Thats hearsay tho so don't say I said it as absolute fact .
I did see one report of a GTX fitting in a Soprano case.
http://forums.anandtech.com/messageview.cfm?catid=31&threadid=1959556
I did see one report of a GTX fitting in a Soprano case.
http://forums.anandtech.com/messageview.cfm?catid=31&threadid=1959556