I think I need to hear some Senn's then, I don't like overly bright sounding music... I consider the HD280s I own to be so harsh on the high end and so colored and boomy on the low-end that they are good for two things - field production where you just need to hear what's getting recorded on the camera (the reason I still have several pairs of them), and shutting out noise on an airplane, where sound quality comes second to actually being able to HEAR the sound. Brightness / harsh highs are also my biggest gripe re: the SR60, esp. played off my powerbook's built-in headphone jack. One thing I find amusing, I must be like one of 1000 people who actually think my Grados are MORE comfortable than my Sennheiser HD280s lol.
Money is far from my biggest motivation when it comes to choosing a product, sound followed by aesthetic then cost is how I tend to choose audio equipment. I worked at (and now, at a different store, again work at) a Grado dealer, and thus have access to rather, well, shall we say 'favorable pricing' on them, so much that I would guess I could buy RS-2s or even RS-1s maybe at close to or less than the price of 650s, and 325s easily for less than 600s, so the fact that many (including myself) feel Grados are decent but overpriced is not an issue either.
I'm not terribly interested in changing to another headphone amp right now, as I just got the X-Can a little while ago, and I do like it's sound. I plan on upgrading it with an X-PSU (and upgrading the power cord on that) shortly, after I pick out a headphone... so with that in mind, will the Sennheiser still be a good match? I'm not terribly worried about soundstage, just a really enjoyable, smooth-yet-detailed sound. If I want soundstage, that's what I have my livingroom rig for - I just really want to have a listenable, relaxing yet gripping sound when I'm stuck at my computer doing all-night graphic design sessions or film editing work.
The music I listen to is mostly (75%) electronica, some pop / hip-hop with an electronic flair such as the Gorillas, a smattering of jazz - Miles Davis mostly, modern and classic rock such as Rush, Sponge or U2, and classical (most of that being stuff like film scores). Artists like Air, St. Germain, Paul Van Dyk, Propellerheads, Moby, Massive Attack, System 7, Bjork, BT, Mazzy Star, Faithless, Sarah Harmer, Ryan Adams, Aimee Mann, Beastie Boys, Antiloop... ok, you guys don't need my entire collection lol.