Any thoughts on EL 34's as opposed to 6L6's in a 100watt BM HRM? My BM has 6L6's with transformers that can handle the conversion to EL 34's.

Thanks blues-

I've heard that about the D-style - that the power tubes don't make that much of a difference. A tighter bottom could be better though
I always thought that EL 34's had more a pronounced mid-range than the 6L6's but I guess it's not that obvious in this type of circuit.

I have a 50w HRM, it has a pair of old stock Siemens el34's in it, bias is currently at 33-36mv, not a perfect match between those tubes.  It goes into a 1/15 using an old Jensen Vibranto...it sounds absolutely wonderful clean or dirty.  I would say that the mids are more, bass is less than a pair of 6l6's.  Gorgeous upper mid harmonic bloom with the el34's.  With the bias set hotter, around 39-42 it goes into harmonic feedback/bloom sustain at slightly lower volumes, along with slightly less top end and more bottom/lower mids.  I stuck some pearl tube coolers on them as well as the preamp tubes, they really do work...both for cooling and slight microphonics reduction.

I have both winged C el34's and JJ e34l's.  I find that the winged C's have more treble response overall than the JJ's, my ears prefer the JJ's in a D-style amp, but I'm sure if you biased them a bit hotter that the Winged C's would sound fuller in the mids and bottom.  I know that their 6l6's benefit from a slightly hot bias as well. 

As far as increased heat from hotter bias is concerned, I'm really sold on the tube coolers thang for power tubes.  I have both IERC and Pearl types.  Apparently in the 50's cold war era some pretty thorough research confirmed that when regular tube glass gets very hot, that it becomes more porous than when cold, lets air molecules pass through, compromising both quality of vacuum and overall tube life...significantly.