TechPowerUp posted a review on the HiFiMAN EF100 Headphone Amplifier & DAC
A quote from the article:
HiFiMAN has a reputation for producing great headphone amplifiers. Today, we take a look at their newest do-it-all headphone amplifier & DAC combo with an on-board T-amp. This all-encompassing device features a class A/B headphone amplifier with a tube input stage. Despite all its features, it sells for $499, which is quite impressive.HiFiMAN EF100 Headphone Amplifier & DAC @ techPowerUp