Why do some model names use "MKII"?

Like kurt-tank said , it's just a newer version . Some call it mark 2 some add a letter or number some manufacturers give it a new name but it all means the same .

This also opens other doors, Upgrade your MK1 to a MK2. You really won't know what you were missing till you hear a MK2 whatever. Now there will be slight sonic difference between an MK1 upgraded to a MK2, than a brand new Full MK2. They might even offer a Signature Series MK2 for only 5k more. What a crazy hobby.

I think that many do pursue the ceaseless pursuit of improvement, sometimes parts become unavailable and new one's must be used. However, I do think that the basics of great preamp and amps design is pretty well figured out and has been for many years, though there have been some improvements in passive parts. So yes, there is a quest for improvement, but there also is a very power marketing reason for new models on the showroom floor.

Mark II was the second king of France.

Merovech.