Ill give it a go since no one seems to want to,,, currently I own a stiletto deuce but used to own a Rectoverb combo. I have found that some of these tubes seemed to perform better in one or an other.
Im sure you know this already but I will mention just in case that you will need to make sure you get tubes that work correctly in your boogie amp.
There is no bias adjustment so this is imperative. Make sure your local dealer knows exactly what hes doing. If your unsure of this go with dougs tubes or Eurotubes,,, they will set you up right.
First off I have never tried the EH el34's although they are the cheapest.
Ill say right off the bat the svetlana or SED c winged el34's are a very good tube thats been put through the test of time. These tubes seemed to sound the best through my ROV. They also make c winged 6l6 which are also known to be excellent.
The mullards you are talking about most likely are the reissues otherwise these would be very expensive if they were NOS. I never tried them in my ROV but do currently own them and swap them in and out of my deuce. They are a nice tube but to me nothing very special.
I will make mention of one other tube worth mentioning that I currently use with my deuce and used with my ROV. These are the JJ kt77's which are a direct replacement for the el34's. These tubes sounded just as good as the SED's with my ROV but are the best sounding tubes I currently own that I use with my deuce. Both Eurotubes and dougs tubes carry these.
Honestly the only way of actually coming to any conclusion for yourself would be to try all of them out. Ive done this with many tubes already and my opinion for you would be to go with the SED c winged right off the bat,, I think you would enjoy these for sure.