With the 12bh7 tubes, on the lowest gain setting (0db), there is an audible hum in my CIEMs (JH Audio Lola). To be fair, they are 16ohms and have 105db of sensitivity. I don't have any hum with my Arya's, which come in at 35 ohms and 90db.
I have listened to both the Level I and the Level III. When I heard the Level I it was pretty early in its break-in cycle so I don't think that it can be compared to my Level III which has 800+ hours on it.
I always struggle with the "is it worth the price difference" question. I struggle with this mostly because I feel perceived sound characteristics and the marginal value of one's dollars are both so subjective....