After reading head-fi.org and some pestering of audiophile friends,
I've found an enthusiast shop not too far from where I live, with the
following headphones in the $100 - $200 bracket:

Sony MDR-CD580
Sony MDR-V6
Koss Pro 4aa Titanium (the only non-portable Koss I could find)
Grado SR60
Grado SR80
Beyerdynamic DT931

Most of my listening is stationary, to melodic/experimental rock
(Within Temptation, Dargaard, Arcana, Stoa, Lacuna Coil...) with some
hard rock (In Flames, Rammstein, Evergrey, Monster Magnet, Rob
Zombie...) and electronica (Delerium, anything from Ministry of
Sound...) for good measure.

I have an old but decent amp (Marantz FM-80), and I tend to feel that
Sennheiser headphones in this price-range have weak bass and even
weaker treble.

I'm not sure I will have opportunity to trying out the headphones
before buying, so - which ones of the above would I be most likely to
like?
From what I've read here and at head-fi.org, I'm thinking the Grados
might be a good bet?