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.