Tim liking the Mullard sound does not surprise me. Most of his stock tubes are most characteristic of the Mullard sound - very full bodied and warm at the expense for clarity and extension. His stock tubes are actually quite good if that's what your after.
I've just put in a pair of 7308 Holland Amperex NOS tubes and have about 30 more hours of burn in time. So far, everything is excellent. The only quibble is the bass is a bit bloated but this hopefully will tighten up with the burn in time. Otherwise, I may have found my perfect tube. If bass doesn't tighten, I will try one Amperex and one Siemens to see how they blend. At least it is really fun! Great CD player though.