You make some good points, Billy. But I'm not saying that housing doesn't make a huge difference in how a headphone sounds. I'm saying it is difficult for me to swallow that the drivers from the SR225 to the RS-1 are the exact same.
As far as your button theory goes with regards to brightness levels in the 325i and MS2i: if that is the case, then the newer, buttonless RS-1 should be significantly less bright then their most recent (lighter wood) button'ed incarnations.