I'm now 11 hours in with the Syl 3DG4 and shutting it down for the morning. The tube sounds like it could use some more play-in. Maybe some 40 to 50 hours. Currently, lacking a certain smoothness, refinement and finish to notes. If the GE 3DG4 is any indication, perhaps the tube will come around shortly. Still, if it's going to compete with the USAF-596, it has some ground to cover.
Not sure about a European equivalent. Time to breakout your Goog-fu!
There is no European equivalent the only one I would try is the GZ37 it is Indirect heated and 5 volt so it won't sound the same but
it can handle the current. 350ma into a choke input load