Etha's have the .693 as standard the same as the Etek's, its the geos and egos that come with .689.
I wouldn't bother buying a different barrel for your sound signature, you'd be better off with a shaft 4 boost kit for performance.
I wouldn't bother buying aftermarket bolts, especially not from techt they will just F*** your marker up
in all honesty its a waste of time and money trying to reduce the sound of your etha, you wont even notice the difference, its still going to make a loud bang when you pull the trigger.