I heard the less expensive (only $30K?) Boulder monos at my dealer a while back on Dynaudio Temptations and Wilson WP7s. The thing that most struck me about the Boulders that I remember to this day was that I had never heard such detailed, textured, "fast" deep bass from an amp before in my life, and I have heard the Levinson 33s on Dynaudio Evidences. While I think the bass from a Lamm hybrid amp might be a little more more natural to my ear (definitely fuller), given your stated preferences I do not think the Boulders will disappoint you in the bass.
Boulder monoblocks
I am very interested in the Boulder monoblocks which look very impressive and have very impressive specifications. However, there are only a few serious reviews published on these amps and for $55,000 there are many options. Essentially, for me the most important quality of an amplifier is its bass performance, I like bass that is ultra fast, tight, controlled, and with lots of slam. Another amplifier I am considering are the giant Mark Levinson No. 33 Reference monoblocks. I heard them at a local showroom and thoght that it sounded amazing. I am wondering how it compares to the Boulder monoblocks. Anyone who has had experience with the Boulder monoblocks I would appreciate your comments. Thanks.