Farthest from the power tubes is the HBE/boost tube. The next is the BE and part of it is clean. Then the cathode follower and then driver tube. Recommended tubes are tungsols in the first 2 slots. Chinese preamp tubes in the next 2 slots and finally jj el34 or e34l tubes. You can buy tested to my spec tubes from Valve Queen. Hope that helps.
I'm loving my BE100, but its always worth trying out some tubes - Ive got some TAD's, Tungsol (Inc Gold), JJ's (I wont use these as Dave should know) and some Sovtek's in my spares box.