Well, lightning strikes twice Herman.
You are again 1000% correct. Very good advice you gave, and as I don't know anything about the amplifiers listed, the line about contacting the manufacturer is key. 50 mA may be a good starting point. Or, it may not be. You should really ask the designer if at all possible.
I often like to set bias on the high side, as I find it imparts a lusher, tubier sound. Of course, you will go through tubes faster. Some people don't have that taste. Use the manufacturer's specs as your baseline, and then play around a bit later to learn more about your amps.
Myraj, some amps are to be biased using current, some voltage. The tube does play into things, but the design of the amp itself comes first.
Some amps are autobias(very easy, but not always best if you want to run different output tubes), some like Conrad Johnson use an LED/srewdriver(very easy), my Atma Spheres have an easy way which would take too long to go into here, maybe the majority of amps require you to hook up a volt or ammeter and perform the adjustment(like your amps), and then there is my Jadis. While most Jadis are autobias, I have a brilliant system where I need to take the amp apart, use two meters, adjust one setting, do the other(which throws off the first), then go back to the first, then the second. Ah, the French...