Here's a running list of electrostatic amplifiers our team has used alongside CRBN2 with good results:
Please note: Although the Stax amp listed has the "pro bias" of 580 volts and will work with CRBN2, there are some (older) Stax amps that have both the original "Normal" (230 volt bias) and the "Pro" (580 volt bias) sockets. The CRBN and CRBN2 require the use of a 580 volt socket to work properly.
Stax SRM-700S (or T)
https://staxheadphones.com/collections/amplifiers/products/driver-unit-for-earspeakers-srm-700s
Mjolnir Audio Carbon/KGSSHV
https://mjolnir-audio.com/electrostatic-amps/
Linear Tube Audio Z10e (also works with regular headphones)
https://www.lineartubeaudio.com/products/z10e-electrostatic-headphone-amp-integrated-amp
Headamp Blue Hawaii SE
https://www.headamp.com/products/blue-hawaii-se
Eksonic Aeras / T2
iFi iCAN PHANTOM
https://ifi-audio.com/products/ican-phantom/
(note, we recommend the following settings with the Phantom:
Malvalve Headamp 3 MK4 (also works with regular headphones)
https://www.malvalve.de/Headamp3-E.htm
WOO Audio WES
https://wooaudio.com/amplifiers/wes
WOO Audio 3ES
https://wooaudio.com/amplifiers/3es