I tried the Violectric V280 connected both balanced to my Chord QBD76 DAC and single ended to my Hugo 2 using HD800S's, Beyer T1 Gen 2's and my Beyer T5P Gen2's (all balanced and 1/4" jack from the V280) and it was the worst headphone amp I had ever listened too.Have you ever looked at Violectric? I have one of the simpler models (V220), but they have more fully featured models and even with a DAC included. The sound is phenomenal and they can deal with anything from IEM's to 600 Ohm monsters.
Even the Beyer A2 (which I had at the same time) was better.
I didn't have my GS3000e's when I had these tow amps so don't know how they would have sounded.
My Hugo 2's headphone amp was far far superior to the V280 and A2 even driving the 300 Ohm HD800's ! And my GS3000e's sound better from the Hugo 2 than both the HD800S, T1's and T5P's. So sold the V280, A2, HD800 and sent the T1's back to the shop. Kept the T5p's.