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