I am running the 6V6's and GZ34's in my triple rec and I love the tones I am getting from them. I also like the sound of the 6L6's but I found myself competing with the bass and I wanted tubes more pronounced in the upper registers. With the 6V6's I have acheived that. I also like the fact that the 6V6's tightened up the lower end and removed some of the slop/sag/mushiness associated with 6L6's. I was looking for a tone similiar to Petrucci and this is what Bob recommended to me also. In addition I purchased the high gain front end kit which I feel greatly improved my clean tone. In my opinion the clean channel is the weakness in my TR, but the combination of these tubes have resulted in the best clean tone I have got from my TR.
Hope this helps
FYI - I don't know about the Dual but Bob instructed me to use the EL34 mode when using 6V6's. No doubt he will give you all the info you need should you choose to purchase the 6V6's.