In testing out a bunch of Grados, I liked the SR80s a lot better than the SR60s. I didn't find too much difference between the SR80s and the SR125s. Though after I listened to the SR225s, the SR80s and SR125s just didn't cut it and the SR60s really fell off the radar. Though the SR225s run new ~$200 which is higher than you want to spend. Oh and then I decided why not and listened to the RS1 and RS2 and you can really hear a difference, but them you're talking new $400+ headphones and well there better be a difference for that price. If I buy a pair of Grados, I'll probably go with the SR225s. (Though there weren't any Allesandro series MSs where I went to try them out, so....)
For under $100, the SR80s are a good deal with regards to SQ...just don't go listening to the SR225s or higher or you'll get the Head-Fi bug, called upgraditus.
PS I decided I wanted closed cans and went with the DT770/80s and Machine Head's The Blackening really sound good through them...and now that I know they can be improved before long they'll become V3 Darths