Samhar, thanks for your response. I appreciate your honesty in admitting you had made a hasty judgment,a lot of folks would not have done that. So for that kudos to you! The only thing I was asking you to do was make a fair comparison.
When I started in this hobby 25+ yrs. ago, all I wanted to do was hear good music through good equipment( or at least the best I could afford) In that time, I have found that there're things (tweaks)you can do to improve the sound of your system that are cost effective or not as expensive as going to the next component in the upgrade path. Inserting good tubes(Nos) is one of them and the 6h30 dr's are an example of that.
When I decide to participate in one of these forum threads, I do it only to impart my experience and knowledge( what little I have)and to help someone gain the same benefits or improvement in their system that I have. I think that's what this forum was created to do and I think that's what most folks who participate intent is as well.
Unfortunately, I think most folks who don't think that the 6h30 dr's make that much of difference have only tried them in amps (and I will admit that in amps the difference is not as dramatic) or did as you did made a rush to judgment but in linestages and preamps, the difference is as you put it significant and not by a small amount!
I hope that others will benefit from your experience as well.