I have the Blue Hawaii too. It is a very good energizer/amplifier. The build/delivery time was pretty long (18 months or so). It has worked flawlessly for me. I replaced the stock tubes with some telefunkens that a friend gave to me (he brought over 4 different sets of vintage tubes and I got to pick the ones I liked for sound). I use it to run 007 Omega II phones (I heard the amp with 009s, but, I prefer the sound of the 007s so I've stuck with my now quite old phones). This amp sounds really good running other phones, like Sennheiser HP 60s, but, either the plugs on the phone or the jack on the Blue Hawaii have to be modified to run the Sennheisers.
Electrostatic Headphone Energisers
I use a Stax L700 Ear Speakers with an 006T Stax Energiser. I'm very happy with it, in fact I think the L700 are astonishing, I won't be changing them.
Just wondered about upgrading from the 006T and where to go, to get a real improvement. The obvious answer is the 007T of course and that's a possibility. There are other choices too, Trilogy do an Electrostatic Headphone amp and there are the units from Mjolnir Audio in Iceland. Any thoughts guys?
I suspect any suggstions are going to be costly for me now I've retired, but I can always look out for second hand units.
Thanks