No sorry, my headphone collections pretty limited! Highest I have are my AKG K712 (60ohms)...
You should be confident with the measurements though, I know it might be hard to imagine how loud the numbers really translates into but, according to your headphone specs (600ohm, 96dB/mW), the essense ST outputting 60mW into 600ohms should be sufficient.
If you're still weary, I'd go with cel4145's advice and get external DAC/amp with a cheapish soundcard for the dolby virtual surround. The Schiit Magni2 for example can output 130mW into 600ohms, which is more than double of the essense ST.
"I can spend up to 200-300 bucks, so the ZxR is affordable. Could it drive the the 600ohm Beyer?
Also, I could exchange the 600 ohm version for a 250 ohm one. Should I do it? Do they have similar sound?
I use headphones mainly for watching movies, so a clear dialogue is important"
My $60 FiiO E11 can (just barely) drive 600-Ohm headphones, at max volume settings.
So I think it's better to find a amplifier that can drive 600-Ohm and do it well.
So maybe read up and ask on this thread about what to get to drive 600-Ohm and drives them well.
I think you should get something to provide a DAC function (sound card or USB DAC) for around $50-$60 and spend all the rest of your audio budget for an external headphone amplifier.
Or maybe get the SB-ZxR and try it with the DT880 600-Ohm, it does not work well, then swap the 600-Ohm for the 250-Ohm version of the DT880.
The 250-Ohm and 600-Ohm are fairly close in audio quality (I own both).