Shure SHA900 portable amplifier suitable for high-spec in ear headphones, including Shure SE846. MSRP for new is £1049. This amplifier is several years old but I have only used it for around 10-12 hours. I do not have the original box and packaging but will offer it as pictured with USB-A-to-mini-USB cable, audio jack-to-audio jack cable, and lightning-to-mini USB cable, as well as Shure brand rubber band to conveniently attach the amplifier next to your mobile phone. 

(It charges via mini-USB). Input is through audio-jack or mini-USB, output is audio-jack. 

"Portable listening amplifier offers enhanced audio control with DAC conversion for use in-line between digital audio sources and headphones. Features include 4-band parametric EQ and the ability to process both digital and analog audio sources."