Maybe Shure 940? By all accounts like the 840 but with bass tuned down and midrange brought into focused.
Well you're all over the place with those choices... you've got full sized, open and closed, portables and not... based purely on sound and personal preference I would go with the ESW9a.
Really try to audition 325 before buying them. They take the typical grado sound and up the zing factor by a bit.
standard recommendations:
Senn HD280 or HD380 (these are hard to beat for isolation)
Audio Technica M50
Shure 840
Most comfortable headphones that I've tried:
Phiaton PS500
Senn PX100 and PX100-ii
B&W P5
AKG K240
I think the 600/650 would be a good upgrade, though personally I would consider a different brand just to play with different sounds. If you like Senn though, by all means stay with what you know and like.
You might consider something like an AKG K701 or Audio Technica AD900/1000/2000
Wow, you've run quite the gamut of headphones there... random suggestions:
Shure 940
Smeggy Thunderpants
Pioneer HDJ-2000
It isn't a *must*, but it highly recommended. It's difficult to get good volume and bass control out of them otherwise.
The e9 will be just fine.
The prices fluctuate all the time. Just wait for a sale and the 600 ohm will drop sooner or later.
Given the college environment, you'll probably want to keep noise out just as much as preventing it from leaking out. I would recommend the Sennheiser HD280, which is the absolutely king of isolation short of iems.
As far as "safe" recommendations go though, the PX100 is a great choice
Now if only they could have maintained that same warm fuzzy sound in a closed container.