Can I drive these with a Sennheiser GSX 1000?
Yes, but not as good as other amps in a similar price range
I would only suggest the gsx 1000 if you needed a mic in or really really wanted those dsp effects
I tried it with a t50rp mk3 pre-argon mod. It was under powered. Max volume resulted in just enough to hear music, but I wouldn’t use it with that amp.
Kinda what I would expect.
You can get a liquid spark + d10 for around the same price and be much better off
Or if you needed an option with a mic, if you can find one, the burson play would fit the bill