ARC vs Atma-Sphere and ARC vs VTL Amplifiers

(Sorry in advance for the long post.)

While I'm particularly interested in the Atma-Sphere MA-1 and the VTL MB-450, I'm interested in learning what sonics users have experienced from the tube amps of all three of these manufacturers. I am most familiar with Audio Research Corp's products so they provide a good reference point for me. I think ARC has made some great amps, so if something is really compettive with their products or better than their products, that would be impressive.

I realize that the models don't all sound the same within a manufacturer's line as designs can change between models and over time. For example, ARC has ebbed and flowed and evolved over the years; their current amps with JFETs seem to elicit somewhat different user comments than their earlier all tube models. And of course the speaker load can make a difference.

Having said all that, I'm very interested in what differences Audiogon users have heard in direct A-B comparisons of ARC vs VTL and ARC vs Atmasphere, and if possible, it would be very helpful to know which amp models and which speakers were heard in the direct A-B, or which amps with what speakers were the basis of the comments if the comments weren't the result of a direct A-B.

While it is valuable to hear a reviewer's qualitative descriptions (more air, more low end extension, etc.) it's also helpful to know how much more or less of these things were heard - just a smigdeon, a noticeable amount, a day and night difference, etc. Generally, I think most Agoners would rather save some $ than just a get a barely discernible upgrade; but if something really takes a system to another level, then sometimes it might be worth spending some $; at that point, it becomes a matter of how many more $, but presumably at least there's a notable difference to be had. (I realize everything can be relative from one user's perspective to another's, but the idea would be to describe both the differences in sound quality and the amount or size of the differences.)

If any Agoners have any comments along these lines regarding ARC vs VTL and ARC vs Atmasphere it would really be most appreciated. It is difficult to find local demos so the ability to get a user's first hand experience "here" (on Audiogon) is the next best thing to "hearing" (the real thing). If nothing else, it helps home-in on the finalists and then maybe it would be worth traveling somehwere to check out finalists first hand.

Thanks very much to all the Agoners who make this such a great forum.