I have the Alessandro MS-1s an I use them all day at work.
let me see if I can answer your question regarding sound leakage.
short answer is YES. they do.
but to give you an idea of how much they leak, just keep your headphones on the table and listen to any song. the grado would leak maybe 80 percent of the sound OUTWARDS as much as it does inwards.
for me its not a problem. the MS-1s are pretty dynamic compared to the philips 890 I had before. so music retains all of the percussive detail even at lower volumes. I dont see the NEED to turn up the volume unless I come across a really rocking song. also, I can hear the phone ring even while playing music, thats a BIG plus point in my office.
to sum it up, it leaks sound, but it helps me keep the volume at reasonable levels so as not to disturb co-workers.
Helps me keep my hearing till I reach my mid thirties
I'd say go for the best 100 dollar phone, REGARDLESS of open or closed.
just my opinion of course.
EDIT: just re-read your original post.... if your roomie is in another room open headphones are NO issue at all..... trust me just go for the best phone within your budget, regardless of open or closed.