Lamm LL2 preamp VS First Sound 4.0 MKII preamp

I can't comment directly on their synergy with the Lamm amp, but I've heard both the FS Dlx Mk2 and the LL2 pre-amps. The First Sound is superior, IMO.

Can't comment on the ML-2, but I have used the LL2 with my ML 1.1s while my Jadis was in the shop. Excellent combination, though a little richer than neutral in the bass. The Lamm has dual volume controls, by the way, though I can't recall if they're stepped attenuators. The Lamm L2 preamp would be a more refined performer in every respect, probably worth the extra money for a used unit, with those amps. There are plenty of other excellent preamps you can use (my Jadis is exceptional with the Lamms), but at this level of performance your personal preference will play more of a role in deciding than any huge differences between the different units.