Great choice in my opinion I look forward to hearing your thoughts on the PS500e. Out of curiosity which Grado's have you listen to at this point?
Unfortunately, I have only owned the RS80e, so I won't be able to compare apples to apples.
What I can say is that the 80e sounded great. Vocals really shined on them but I felt like they were a little thin on bass. That said, I don't particularly like a lot of bass...I listen to mostly rock and some classic rock.
I recently auditioned the M50x and found them way too bass heavy for my likes...so that might give you a baseline.