I have spent the weekend swapping tubes in Carr Mercury. I use a KT66 power tube. While I have spent a lot of time figuring out what I like in V1 (I'm torn between the Tung Sol 12ax7 reissue and the JJ EC803S), and the Mullard CV4024 kills in V2), I haven't given V3 much time or attention -- I just stuck a new JJ ECC83S in there and moved on. Does it really matter all that much what I put in V3? If so, why? Thanks.