I'd like to weigh in about the MKIII mod that allows you to use 6H30Pi tubes.
I did the mod a while back (I believe this thread was on page 50 something at the time) and put in the EH 6H30Pi Gold tubes I had purchased for a pretty high price from Yen Audio (who has the all the great tubes, and THE best customer service, but certainly the harshest prices). Unlike a lot of people in the world I don't suffer from the condition that effects a person brain to believe that the more expensive something is the better it absolutely has to be (MRI scans have shown that in some test subject's brains their brains actually react and the subject's thinking patterns change when given two exact same substances but told that the second substance is the more expensive one - like wine for example - making the subject believe that one tastes better even though it's the same wine). So, back to the tubes I've switched out the stock tubes and am now listening to these new, fancy-shmancy, expensive tubes. On first listen I can straight out say that the stock tubes after decent burn in are better than the brand new, un-used Golds. But of course we have to go by the burned in sound. So, I use the Gold's for quiet a while and believe that they do in fact get better. They seem to become warmer (or "musical", if you will) but in no way add to the sound stage or expand the low or high end. So, even after burn in the Golds, when in came down to it, simply added mild warmth to the amp. For the trouble of the modding (and the chance that you'll burn something out even WITH the mod, as the last few pages of this thread have indicated) and the ridiculous price of the new tubes I can honestly say it is, in absolutely no way worth it. And, I'm not even saying, "If you have the money it might be worth trying". No, I'm saying if you bought an MKIII you'd be straight out wasting you time and money to get 6H30Pi tubes.
Lastly, I CAN say that while the stock tubes may not be as warm as the Golds were the difference in warm is next to negligible and I've found that the sound stage is about that much better on the stock tubes. The switch is basically an equal trade of sound stage for warmth but very, very little anyway. Not to mention the whole unit is cooler with the stock tubes.
Needless to say I put the stock tubes back in and my MKIII is staying this way: Stock power tubes with Sylvania 6AK5 Golds tubes.