How would you describe their sound signature in general terms with some details? Anyone compared comparable models?
I am just interested, not going to have to choose anytime soon. I heard LAMM quite some time ago and probably not their best; very much liked the sound. Never heard VAC.
I have Lamm M2.2 and love it very much but there are a few things to consider. M2.2 is certainly considered a great high power amps but considering choices of speakers nowaday and Lamm's relatively low damping factor, it may or may not be the best amp for your speakers. I had a pair of Usher Be-20 and a few amps went through my room during that time. Older pair of Spectral DMA 160, Jadis JA200, Plinius SA 103, ASR Basis Exclusive II and then Lamm2.2 To my ears, Lamm has the best midrange, a little dark on top but well extended (more so with US Amperex pinched waist 6922 than pretty much every other 6922 tubes I tried, other tubes that I tried such as Mullard, Mazda, Gold Aero etc. Lamm bass is deep, tight but does not have the punch or control Usher's dual Eton drivers nearly as well in comparison to Spectral or ASR. Even Plinius SA 103 is a touch better in this regard. However, Lamm's lower damping factor seems to match my current speakers, Magico Q3 much better. Unfortunately I don't have a chance to hear Q3 with any other amps beside Soulution 710 (but in different room). I actually prefer Lamm as Soulution sounded incredibly clean and fast but does not sound natural to me. I kept thinking that no tympani and bass drum is that tight. I wonder if that might have something to do with Soulution extremely high damping factor (Lamm listed its damping factor as 82, Soulution >10,000 ). I would love to hear VAC but it is not available locally here.
VAC is untouchable in its mids and highs. I have a 300.1a and the detail retrieval, refinement, and smooth nature of the mids/highs is best I've heard. The lower registers are there, just not very pronounced. Very deliberate and tight as can be, but gives the overall sound a tipped up presence unless your speakers are darker/bass heavy. I am only running one 300.1a on 89db speakers with nominal impedance of 6ohms but big swings to 3.7 ohms. The clean, smooth, clear highs and mids, with tube magic on imaging/dimension, is addictive.
Both are great manufactures.

That being said what Kur tank wrote;

"Vocals are just incredible with the VAC! The treble response is even more refined than the Lamm is, (which I thought was impossible, as the Lamm had beaten all comers up until the VAC came along).

I fully agree with this statement and would like to add there are further improvements using two in mono block configuration, will improve the bass and dynamics.

I own MBL 101E's and it's been a long journey trying this and that, once I heard the VAC's Statement 450 mono blocks paired up with their Sig. MK2a pre-amp well it's most defiantly a exspearience that I'm very fortuante to have had and heard which I now own and has gotten me off the merry-go-round.

I have never exsperienced hearing anything like this, not even close.

You can refer to VAC's web site for a more detailed description of such but really it's so dramatic just leaving you with a smiling exsperience.

If you were after a stereo only pce I would want to hear the Statement 450S stereo.