If you are looking for a venue for serious comparison, you'll find it at a hi-end stereo show. Obviously, it may be a while before one actually happens but generally there are most manufacturers of both headphones and driver units. They are worth waiting for if you are planning to make an expensive purchase (even $2500).
Electrostatic headphone amplifier recommendation
Finding a reasonably priced electrostatic headphone amp is proving harder than I thought. It seems like everyone likes the blue Hawaii for my stax 'phones (SR 009) but at $6k! Yikes! I'm hearing mixed things about Staxs own amps, that they can be a little noisy. Looking to spend less than $2500 ( used).