Len,
A few thoughts based on some of the recent posts. First, with respect to the Ref 3A deCapos, I found them to be a bit slow in the low frequencies when driven by the dynamo. I think they need more that 8WPC. Second, it might be worth waiting to see what gives with the Dynamo MK II that Mikirob mentioned. If it is a substantial improvement, it might be worth the wait, if only for the used MK 1's To hit the market. I'm using the Psvane Philips reissues, which are pretty good tubes but with some reliability issues. I bought a quad, and got two usable tubes (which is all I needed) plus a refund on the two duds. I'd try to snatch a pair of nos mullards before they are all gone.
The extra 2 watts may or may not make a difference, depending on which speaker you choose.