I upgraded from an original 17ls to a 16lsII and the difference was amazing substantially more detail and bass control. In my opinion worth the substantial higher cost to upgrade. Although I have not heard the 17lsII the circuitry is very similar to the original series I. The 17lsII is probably a step closer to the original 16lsI but still not in the same league. In my opinion the 16lsII is the better pre-amp over the 17lsII. Better circuitry (6 tubes versus 4) and better parts. Even CJ commented that they used the same higher quality parts in building the 16ls that they use to build the ART. They do not, however, make that same claim concerning the 17ls. The 16lsII is basically a single chasis ART.