I tried out my PL2500 this morning next to both 780's
The PL2500 are still enjoyable, but the differences I notice which make them less enjoyable than either 780 is the decrease in bass impact, and the withdrawn mids. I still wont call the mids sucked out, because sucked out needs EQ (Darth Beyer shallow cup, Stax Lambda Pro). The 2500 mids are closer to a Super.fi 5 pro while the 780 mids are more like a Triple.fi 10 Pro.
I've had several people ask about the sound signature, is it more like Grado or Sennheiser. The answers to that are in the other HFI780 thread
So what's the word on the new Ultrasone HFI-780???? so just read it all, listening to the people who own them, not the speculators and spectators.
In a nutshell, 780 are fast and energetic and forward vs slower and mellower HD600, but they are not the Grado "in your face" nor as "deep" as the HD600. However, the right source, amp and cable can get the HD600 to sound like that (fast and energetic). For instance, my re-cabled HD600 and re-cabled RS-2 actually sound very similar. Yet a stock HD600 vs stock RS-2 is more different, with the more energetic forward sound going to the RS-2. However, you would not mistake a 780 or HD600 or RS-2 for one another if you were blind folded, whether stock or re-cabled.
The 780 have more bass and treble than my re-cabled RS-2, but have a wider soundstage and are less in your face than the RS-2. But my recabled HF-1 have more bass and a deeper sound stage than the RS-2, but not a lot wider. So, even among Grados the sound can be different.