Hello all -- after three months and 1,100 miles of ownership on my 2005 K12S -- I'm now on my third and hopefully final exhaust slip-on. I bought the bike pre-owned in great shape and with a Scorpion can on it, which sounded ok. I wanted something a bit more aggressive-sounding (ok, a LOT more aggressive-sounding) so I started off with a Remus Hexacone. That lasted about a month. Sound was too weak for me -- it was a slight gain over the Scorpion but not what I was looking for.
Ended up installing the 19-inch Remus Powercone (titanium finish), minus the insert. HOLY CRAP, I'm in love.
This thing barks and snarls now, which is exactly what I wanted. Plus the BMW dealer I ordered the pipe through, the guys there really liked it, as it was the first 19-inch setup they have seen (BMW Motorcycles of Plano, TX).
Remus advised if I was running the stock BMW luggage, which I am -- to get the heat-guard tape that you install on the bottom of the right-side pannier. Although I broke a blood vessel in my neck having to pay a stratospheric BMW price of $25 for a 4-inch by 6-inch piece of foamed foil, I installed it on the case, figuring that was better than melting the bottom of a near $400 piece of luggage.
Incidentally, Remus advised the 19-inch powercone was the ONLY powercone that will fit with the stock BMW luggage for the K12 -- the 20-inch and 22-inch units would hit the bottom of the luggage.