Lt Do you run your ming at 50%? Ive always worked on the 70% rule and biased my amp to around 350V, Im guessing the ming will be running at about 250ish? Im glad your an expert on WAD's, the Kit6550 is on my 'to do' list I'll call on your experience!! Ive always found 6550's more 'modern' sounding than the older KT's & EL's, slightly cooler but more clinical with abit more (dare I say) prat, a valve for the SS generation!! Im pretty certain Ive yet to hear a properly set-up 300b as Ive always been left thinking "well?".