Balanced headphone amps

Hello all,

I'm interested in trying a balanced headphone amp with my Hifiman HE-500. Has anyone out there paired a Schiit Mjolnir with these headphones? Any other favorites you'd like to brag on?
CEntrance HiFi-M8 for a portable amp/DAC

SPL Phonitor 2 for wonderful balanced amp with loads of power to drive any headphone
Thanks, Shaker, I've read several glowing reviews of the SPL Phonitor, but it will break my bank. The Mjolnir is intriguing for that reason.
I have something called the Headroom is quite wonderful. The biggest problem is the on/off switch is in the back

I also have a Headroom amp: an antique Little. My biggest problem with Headroom products is they are no longer in production. Too bad for headphone users. long as they work. My Blockhead has the upgraded every things...the sound is much better than my big speakers. Never had any problem at all with it. I use Sen. 650's with the balanced Cardas cables from an Ayre preamp.
I have and highly suggest the Bryston BHA-1. It has all the flexibility that you will ever need and sounds great. Plus you get a 20 year warranty.