I'm considering getting a FA STEN, leaving price out of it, as I know I'll pay a lot $9,000 plus . What should I look for? I've seen a few online that come with 2-3 xtra barrels, and I prefer the wire stock. I believe that's a mk II ? And would like the barrel threaded, but I guess I can have that done separately if need be. How do they sound suppressed? School me!