I really like the K & K Pure Western system that mounts under the bridge plate on just about any acoustic guitar. It has a very woody, natural balance without that weird "quackiness" that most under the saddle pickups have. The only flaw I have found is a very slight roll off on the top end, but that just be on my guitar (a late 1930's Gibson L-OO). You can compensate for this roll off by EQing it up just a tad on the top end. I played a gig recently sharing a bill with another player who had an under the saddle Highlander pickup on a similar '30's Gibson L-OO and the K & K just sounded way more natural, retaining the acoustic tone.
I also use a AKG C1000s condenser mic that the previous thread mentioned (I use it for my National resonator guitars that have no pickup) and it adds a bit of acoustic air to the overall sound, but if I had my choice between the microphone or the K & K I would go with the K & K as it has a more immediate, crisper response than just the microphone (and more volume without feedback). That AKG mic works great for a resonator guitar as those reso's put out a lot of volume, but I have a little difficulty getting the sound I want on a regular acoustic with just the microphone. Amplifying a twelve string really should not be any different than a six string.
One nice thing about the K & K is that they are very reasonable...my local guitar shop charges $150 including installation! You can't beat that. It sounds best with a preamp, but it actually sounds pretty good without one, which is pretty amazing.
That Fraulini 12 string is a wonderful guitar. A friend of mine has one and he has let me borrow it for recording. I love it! If you go to my My Space music page listed below you can hear it on the track where I play Blind Willie McTell's "Mama "Tain't Long For Day" (in G tuning, tuned down two steps in pitch) and there are even a couple of photos of me playing it on that space. Those guitars are featherlight and have a wonderful response. I plan on on ordering one when my finances improve. Hope this info helps.
James Clem
www.jamesclem.comwww.myspace.com/clemjames