Mike's description above is all the more reason why I want so much to hear the Lamm LP2 and the Io Sig compared to my older Io std model. And I only have one P.S.
As Mike describes the differences between the Io's and the Lamm, I can fully understand the balancing act and tradeoffs to find a product with the 3-dimensionality, ambience, decays, etc., vs. achieving a lower noise floor, higher resolution and retaining the dynamic contrasts as well. I have been going through this same exercise with line stages that seem to be even more critical than phono stages. It really is tough to find it all in one unit. But it sounds like Mike has found one heck of a unit with the Lamm.
After reading Albert Porter's many posts on the Aesthetix gear and how he has taken his units to a whole new level with a lot of tube rolling, I contacted him a couple years ago to get some advice on what I could do to improve my Io. Changing out the stock Sovtek tubes to Telefunken's transformed the Io far more than the Io improved upon my previous phono stage, the BAT VK-P10. There is so much incredible volume of space around instruments with this tube change. The decays on the piano and percussion was a new experience for me. No matter how refined a product might be over the Io, if it lost a lot of this attribute, it would be tough for me to change. I gotta believe that this is more dramatic than the Io Sig over the Io or a change from 1 P.S. to 2.
I have read much here about noise and bad tube issues and other failing components in the Io, Callisto and Calypso but my Io and Callisto Sig have performed flawlessly with none of these problems. Evidently there was a bad batch of parts and bad set of tubes that have since been resolved.
Even with the tube changes in the Io, there was indeed a little more background noise with my Io over the BAT. The BAT gear has always impressed me in this regard. And yet the Io was significantly more resolving of details I had not heard before in the music.
It can be a pain and quite expensive to go through all the efforts to play with different tubes and deal with the issues of noise, microphonics, reliability, heat, etc., vs. a minimal-maintenance put-it-on-the-shelf-and-forget-it unit like the Lamm, but if your priority is more toward the space and decays vs. the resolution and lower-noise, the Io may be the perfect unit for you. The only way to know for sure is to try each out in your system.
John