When the Stax SR-009 first came out, there wasn't anything on the market really capable of matching its resolution and clarity. Give or take 7 years later, there still isn't really anything on the market that can match the detailed, transparent sonic image only electrostats can provide In terms of positives, the SR-009 are still the most transparent headphones on the market. I've always hated phrases that describe transparency, "it sounds like an open window to the music" or "just the music" due to their vagueness. Whenever reading comments such as...

The SD-1955 delivers very low distortion for the price, and a clean, clear all-encompassing sound to match. Exchanging stock op amps is recommended.

It's transparent, and neutral with a slightly warm tilt. Noise floor is non-existent and great for IEMs. Look elsewhere if you want more bias in an amp.

Not much to say, the HM5 really convenient to use since it's easy to drive. The clamping force is the strongest I've ever felt on a headphone; stretching is advised.