Need advice on amp to drive Vandersteen 2Cs

A Watt is a Watt is a Watt. Tube inches aren't any bigger than ss inches either.

Well I will not say transistor watts are different than tube watts. I will say the rating used to advertise power in the early days is different than today and you have to ask what test they are talking about. Back then I believe they mean you could drive a specified dynamic load all the time with the power but today marketing news-propaganda-speak-sell-the-product-pronto talk means something else. Better to just hook it up and see if you like it and lite a match to the slick advertising. Power is a product of current and voltage and tube amps tend to have less current due to the Z transformer since it's an inductor. Well designed tube amps tend to have massive Z transformers and power supplies.

I would not use a Dynaco ST70 for the 2C as it is not enough power and you will probably produce too much clipping. The 1C however is more efficient and is a very good cheap combo for the ST70. The Min power I would use is 50 watts for the 2c. See the 2C spec. If you use a sub it may work buy you just have to wire it up and see if you like it. EL34s are known to have good mid range.

Just looking at your components I would go with an older tube preamp for about $400 or less. Audio Research Sp6, CJ pre-amp from mid 80s, lots of choices. My first tube pre-amp was a Laz cascode basic I got new for $600. Bad power transformers from several samples. AC 60hz leakage on the little flat transformer, which is why I like ARC. No stupid parts selection like that.