Genalex Gold Lion EL84

I've no direct experience, but I've read good things about them and will probably be trying them in my Music Reference RM10 MK II.

You mean EL 34's don't you? In which case (if you want the ultimate in sonics) I would recommend the NOS Genalex (but VERY expensive!)

JJ currently makes a KT77 that a lot of people seem to like, and they're not too expensive:

http://thetubestore.com/teslakt77.html

Mullard Russian EL34 for Dynaco ST70 and Genalex Gold Lion EL84 for Eico HF81