Amplifier / system matching w/ Vandy 5a

I just sold a pair of Vac 220 monoblocks and replaced them with the Quicksilver V4. At the time I had the Vacs driving the 5A, my Benz ruby 3 had more than enough gain going through the Lamm LP 2 phono stage. Since that time, I have only made the change in amplifiers, and all of a sudden my fairly new Benz (.34mv) does not have enough gain. The input impedandance of the Quickies is 1.5 volts (w/ a gain of 27 db) . My First Sound PD 2 has an output impedance of 1200 ohms. The Vac had a gain of 38 db (unusually high compared to that of other tubed amps specs), but am unsure of its input Impedance. I have put the new ruby up for sale and remounted a Koetsu Red ( they say koetsus are generally lower than their rated outputs ). The red has enough gain, but I would like it to have slightly more. I was hoping that a true .65 mv Shelter 90 x would be just right, against the overrated
.6 mv spec rating on the standard red.
I am also considering the 90x, as I think it may be a better match with the Lamm LP2 and with the system.
Has anyone experienced such a huge difference while changing an amplifier in a system ? Has anyone used the Shelter with the Lamm and its set loading of 40 db ?
Thanks in advance and sorry for the long-winded, multiple question post.