i have owned both, while the 5.5 is an exceptional pre-amp for the money with it's versility, especially with the built in phono section, the Lamm is in another league, sonically.
If performance is your goal, the Lamm sounds more like music, mates well with the LP 2 phono pre-amp and delivers you to another level of naturalness.
Please understand the 5.5 is an excellent pre amp especially with NOS tubes,
and with the remote and phono built in it is a great value, without going overboard.