Modwright LS 36.5 or BAT VK-51SE

If you have it narrowed to 2, get both, return or resell the one you don't like.

Some sellers maybe even willing to let you try for a week with the option to return. Of course, you cannot lowball someone and then ask them to do this for you, but it is reasonable to ask, if you are buying at their asking price.

Well...

If one cannot tell the difference between 3 entirely different preamps, I'm not sure if I would consider that a curse, or lucky.

At least it makes life simpler.

I think these preamps would have a world of difference between them. All good, all different. In the right system, the best out of the 3 could mean the difference between magic or dull.

Greg, I have no information specific to Lamm being noisy with other amps. However, you are correct to be concerned, and you should pay attention to this issue with a demo. Particularly with the Pass which are so quiet, adding a noisy preamp is one step forward, two steps back. If you can readily hear the difference in noise from your listening position in a quiet room with the preamp on vs. muted, then it may nag you in the end. I think noise destroys a soundstage.

In terms of mismatch, also consider that cabling is HUGE in defining bass and upper-end extension (PC, IC, SC). So many cables out there restrict both, or do one at the expense of the other.