Rick
Headphone.com has a lot of really useful info on all types of phones, and even though they sell them on the site they are still pretty balanced (partic if you can read between the lines a bit).
I used to have Grado 60's a long time ago and still remember them fondly. So the 80's should be even better, and well suited to your choice in music. The only issue I had was getting them comfy on my rather large head. In the end I bravely / foolishly bent the main bar outwards quite a bit and bingo, they were comfy. Albeit looked slightly daft / damaged when not in use. In the end I just wore them out with use.
I'm a Sennheiser user in the main now, with both 650's and PX-200's, the former being outside your budget, the latter about £50 so well within. Have to say I use the 200's a lot, maybe you could save some money to spend on a separate headphone amp (if needed)?
Whatever you go for £100 should give you a pretty decent sound. Have fun!
Edit - Drummerman;bad hair day? But your flowing locks look so lovely!