I don't like the Mullard reissue. They are pretty much the same stuff Mike Matthews is also peddling under eh and sovtek as far as I could tell. I've found JJ to always be pretty solid, I particularly like their rendition of the kt77.
Anything between 60%-70% max plate dissipation is reasonable, so using a 25W figure instead of 30W is perfectly fine, many surprisingly prefer a cooler bias especially on amps that have a lot of preamp gain, and at those figures it won't have much bearing on making the crossover notch more apparent, and is ever so slightly easier on the valve. Over dissipation is what you really want to worry about, especially on most Marshall's. The a-a load Marshall tends to use is not ideal for el34's at the typical 470-480vdc plate and screen voltage, especially when the el34's are biased near 70% of their max plate dissipation, so it's not uncommon to see some red plate only under signal conditions but stop when in idle if some things are not put in check. However this heavy loading is a part of the sound. I would play it on the safer side but that's just me. A lot of the older, older Marshall's don't have this problem, because they had less efficient pt's with arguably poorer regulation, which caused the power supply to dip enough under larger signal excursion in order to push the load line below the knee.
