They're the most similar closed can I've heard to the Grado sound. Forward mids, textured bass, and nice treble extension. Some say that the treble is a little hot, but those are probably the same that say the 325 is treble-heavy.
When going back and forth between the 225s and 7506s, the similarities certainly outnumber the differences!
Thanks for the tip... Will definitely try to get a hold of those 7506s...sounds compelling