When it comes to the 2600x vs 2700 yeah i thoghut the same . Thats why i stopped thinking bout the 2600xI'd go 2700 because more core/threads are the future. If they were not the future, we would still be using single core cpu's.
As for the speed difference, that will be less than 10% in real FPS on most games.
NON X version - you can OC if you want - it's very simple to do from BIOS.
Don't be scared of OCing, just don't be stupid with it.
eg 10% OC is very easy on any AMD CPU