well, for those of you who are interested in what I decided to do, here goes...
first, I found a dealer in Boston that had the entire Grado line for me to listen to. I asked to listen to the sr225's, the sr325's, and the rs2's. I found the difference between the sr225's and the 325's to be subtle. then I put on the rs2's. huge difference, and I noticed it right away. (fyi, I didn't listen to the rs1's)
ok, at this point, I know that I've got to compare the Senn HD600's to the rs2's. the Tweeter store in Harvard Square had the hd600's on sale for $270, and they had a full money back for 30 days thing. so I bought them, and went back to the Grado dealer with the Senn. in hand to do my comparison.
I'm not very good at describing sound, but here are my thoughts anyway. The Grados are much more exciting to listen to. They really seem more "up front" (whatever that is supposed to mean), but the sound definitely jumped out at me a lot more than the Senn. cans.
so I returned the hd600's on my way home, and I am now a happy owner of the grado rs2's
while all this was going on, I was checking out prices on the grace 901. Oade was able to sell me an open box 901 that had been used for the stereophile review, w/ full warranty, for 100 bucks less than it would have been. it will be here early next week.
I'm psyched!