AtmaSphere Upgrade from Mk 3.1 to Mk 3.3

I have a pair of MA-1 Silver Anniversary edition amps that I had upgraded to Mk 3.1 some time ago.  I see they are now up to Mk 3.III.  Has anyone made this upgrade?  What did you hear different, and how significant was it?
I only have experience with the 3.3's, but when I was looking at buying a non 3.3 Ralph and Adam have told me, it is a very big upgrade- sound and rebuild-wise(hence, the cost. If I recall, it also affect tube performance. 
Hopefully, others will chime in. I just want to give a quick response.
There is a member who picked up a set of MA-1 Silver Editions and had them updated to Mk3.3. They were previously at the Mk3.1 level, so his comments are exactly about what you are asking:
I see that he is very enthusiastic about his upgrade, but he doesn't get very specific about what the changes were, technically or sonically.  What should I expect from the upgrades, sonically?  I understand the 3.3 upgrade replaces the CCS tube  with a solid state device, and uses its position for a 3d amplification tube.  I don't know what the 3.2 change does, or what effect it might have on the sound. 
My friend had his MA-1 amp upgraded last year and he was very pleased with the sonic improvement.  Sorry, I don't know what changes were employed, but he was also given a new 3-year warranty which is a really nice added bonus.

The update causes blacker backgrounds with a smoother and more detailed presentation. The new Constant Current Source (CCS) has nearly 2 orders of magnitude greater performance- and results in greater differential effect in the voltage amplifier. All the updates from the Mk3.2 level are included in the Mk3.3 level; the Mk3.2 has measurably lower IM distortion, which is audible as smoother sound.