How many tube watts for Vandersteen 2's?

Pubul57, the act of increasing the bias on the tubes has the effect of reducing their output impedance. This will change the relationship they have to the output transformer.

In addition, you have to also consider how the amplifier was designed. For example, many power tubes want to see about 3000 ohms plate to plate. But what if you had the transformer designed to be 3500 ohms plate to plate? You might loose a little power, but now you can experiment with different taps to affect the sound in different ways. This is because the transformer really does what it is called- it transforms impedance. The load that is on the output taps will affect the load that is on the tubes. Especially in the last 30 years, its been a good idea to build in a little reserve to deal with the many 4 ohm speakers out there.

So if in the above case you are loading the 4 ohm tap with an 8 ohm speaker, the result is that the tubes might see a load impedance that is much higher, perhaps 6000 ohms. Now in some cases the amplifier will not be able to make as much power, as the voltage that needs to be made across such a load to get the power is no longer available. But it may not matter if the power thus obtained is sufficient.

One of the best times we had with the Vandersteens
and an RM 10 was when Traveling sales fellow showed up with pair of huge golden gridle Prototype OTL 10 inch tall 30 deep mono blocks.
After listening an hour or so he said so wad do ya think
I said hold on and reached for the bible size RM 10
wired it up, we looked at each other and I said you in trouble....
Its the output transformer
JohnnyR

Old Testament only.

Ok I'm not sure if im jumping in the right way as I'm new to audiogon lol i picked up a nice pair of vandersteen model 2ci the guy i bought them from had a old Kenwood integrated 60w per ch driving them i was impressed with them for $550.00 i thought they were a steal got them home connected them to my Cambridge Audio 840a integrated that I thought was far superior to his old Kenwood integrated i was wrong ramping up the vol to my favorite tracks of  Stevie ray and double trouble the Cambridge was quickly clipping so when reading about the sound achieved with the Vandersteens through tubes i thought for sure i was going to need at least a 100w tube amp but then i here about current?  & output transformers I'm just afraid I'll buy something and be disappointed anyone have a take on primaluna prologue or quicksilver mid monos ??

Hi moronpainter and welcome to AG. 

I cannot suggest this strongly enough- use punctuation. 

So so hard to read posts without punctuation.