The History Behind Viva Linea?


Can anyone here share a high-level progression of advancements in the Viva Linea preamp? In searching for a DHT preamp, this one came to my attention, and literature around it has been minimal at best, but it’s reputation seems to be stellar. 
Research has led me to find that it has gone through many iterations in the last 20 years.

Viva Linea 300 - one of the originals where the power supply was in a big V-shaped chassis

Viva Linea XP - from my understanding the next version. Later models shifted away from the V-shaped chassis

Viva Linea (current model) - newest line in slimmer chassis

Each of these models seemed to vary in power tube configuration - some built in 300B, others in 2A3 or 45. 
Is there anyone that can tell me what is different technically and sonically between these models? I’ve seen some of the first two generations sold at relatively affordable prices so more than anything I’m looking to compare between the first two models and between the XP and the current model. 
I have contacted Viva directly, who guided me to talk with dealers, and none of the dealers I’ve spoken with seem to have the historical understanding of this model. 
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Jond:

Wow, I was interested in this preamplifier and I thought you taking the time out of schedule to mention possible pitfalls was incredibly helpful and thoughtful.
Jond - I want to echo audiofun here. I never intended that you were not being helpful. I think you were trying to be very helpful. It just didn’t answer my question.
Someone is selling the Viva Linea in a nice red color in Audiogon.
You should ask him.  It looks nicely built with that separate power supply also having tubes
https://www.audiogon.com/listings/lis9jda4-viva-linea-tube

Warning, necropost....  I think the OP has the right history for the Linea.  That is what I also found we doing research. I have the current Linea and it is world class in terms of performance.  I have received good support from my dealer and from Viva in Italy.  I also have the Egoista headphone amp and it is also just mind blowingly good. 

I don't know about the issue of not providing support for used products, but there are plenty of highly qualified techs around that could fix any issues should a need arise.