Hi Nigel,
I think the 6l6 sounds best. They are really thight and have good sound for that kind of music. Then I would take the kt66 and at last the EL34.... 
Based on the audio files I would say you have a good sound. But is it reasonable to convert a amp like the JTM45/100 into a hevay amp? 
I would say i go to bed now 
Good night
Hi Fl@shR!Der, thanks for your great feedback,

the amp is a clone of a jtm45/100 i have built, so I'm not so worried about modding it, i dont think i would mod an original,

cheers
Nigel