Atma-Sphere MA-1 amps

I own a pair of MA-1s from 1990, obviously very early in their history. I would be interested in hearing from anyone who also owns or owned MA-1s of that vintage, and either (i) upgraded them to current or near-current specs, or (ii) replaced them with a newer version MA-1. What I am looking for is some sense of a comparison between the old and new, ie to what extent the sound is the same or similar, and to what extent improved.

Interesting. Some questions for the newer owners:

1. Can you adjust the bias yourself? Or is it pre-set at the factory and does not provide for manual adjustment? (Mine have a manual bias adjustment. The sound improves significantly as you push the bias toward the recommended setting, but tubes blow more frequently at that point.)

2. Is there a built-in bias-meter? Does the bias remain steady? I have a digital multi-meter to measure bias, and there is a fair amount of variation in the bias reading before it eventually settles down.

3. How frequently do tubes blow? Is there a simple way to tell which ones have blown? (My eyes are no longer good enough to see the very thin wires in the tubes that indicate whether they are good or not.)

4. Do you use upgraded power cables? Was there a material difference when you first installed them? In what respects?

5. How much of a warm-up does it take to bring the tubes to the prime listening point? I found that it took 24-48 hours to get to that point, so I eventually would leave the amps on for days at a time. Sound was improved, heat was not good, tube life was not good.