Elear/Valhalla 2 a very good combo IMO. The Schiit website says:
"Go ahead. Do things with Valhalla 2 that you’d never attempt with other OTL tube amps. Run low-impedance headphones. Use IEMs. Valhalla 2 is a complete re-imagining of Valhalla, with improved performance, higher output capability, lower distortion and output impedance."
And:
"While most tube OTL amps are really only designed for 300 ohm Senns and 600 ohm Beyers, Valhalla 2 stretches to include headphones that you’d never expect to use with a tube amp. Many people use Valhalla 2 with sensitive, lower-impedance headphones as well."
And:
"Valhalla 2 also adds two important features: preamp outs and a gain switch. Preamp outs let you connect your powered monitors directly to Valhalla 2, to give them some of what some people call “tube magic.” The gain switch gives you better control of both output level and impedance, for better matching to your headphones."