Jon,
I have both 100N+ and LF55 and have compared them under two circumstances:
Bedroom system, driving GR Research Paradox 1 monitors. Bedroom is normal size, 12 x 15??? P1s are about 88db.
Main system, driving GR Research Paradox 3 floorstanders. Room is large, L-shaped, 38 feet long on the long part of the "L". Base of the L is 20 x 16 or so. P-3s are ~ 90db.
In the bedroom, there is no contrast. The LF55 will steal your heart, soul, and mind in about 5 seconds.
In the larger main room, the LF55 can get conjested during large orchestral works while the 100N+ just continues to kick butt. If I was continuing with the P3s, I would have to save until I could do an LF100 (I've just completed my Orions, LF55 tweets, 100N+ on the mids, 100N+ on the bass) and I still have an LF55 in the bedroom system (now driving the P3s). Obviously, my audio budget is way tapped out for now....
Sorry to be brief.. I'm in a scoot right now. Happy to answer questions later.
Peter