Guidostrunk
Headphoneus Supremus
Only one I could find on the web.
https://www.amazon.com/gp/aw/ol/B00CHIJTO6/ref=mw_dp_olp?ie=UTF8&condition=used
Cheers
https://www.amazon.com/gp/aw/ol/B00CHIJTO6/ref=mw_dp_olp?ie=UTF8&condition=used
Cheers
The best amp i have ever heard with the HE-560 is the Yulong Sabre A18 amp. It's discontinued now, so see if you can one second hand or on sale.
The Airist Audio Heron 5 is also spectacular with the HE-560s. Same foes for the MicroZotl-2. The Cayin iHA-6 is also an excellent pairing.
All of these are well within your budget.