The Empy is a warm headphone and mates well with a neutral headphone amp.
I had the following unit and it was good with the Empy.
Matrix Audio Mini i-3 Pro Streamer, DAC & Headphone Amp (headphones.com)
This unit is one of the most versatile pieces of gear I have used. You can stream from Ethernet (best), Wifi, Bluetooth. The unit is almost like a portable headphone amp.
I also tried the Topping A90 with the Meze, but you need the DAC and streamer to go with that.
Topping A90 Headphone Amp for Desktop (headphones.com)
It is also a good match.
The best match was the Benchmark HPA4. It is super clean and so quiet. The Meze love the HPA4 the most but the other 2 were very good for the price.
Benchmark HPA4, silver For Sale - US Audio Mart