Thanks much for your input. I had the chance earlier today to demo some headphones at my local magnolia/bestbuy and agree with you completely based on what I was able to demo.
I don't want to derail this thread with a full assessment of the different headphones that I tried out, as this is a gaming headphone thread and I was just doing general listening with them, not gaming.
But I will say that I did rule out the "on ear" style of headphone. I was able to try a few B&W on ear style as well as both the Sennheiser Momentum on ear and over the ear styles. I just didn't like the fit of the on ear models even with their low weight.
I was able to listen to these models: Sennheiser 558, Sennheiser Momentum (over ear and on ear), AKG K550, Denon AH-D600, a few B&W on ear models, and some noise cancelling full size that I can't remember the name of as I've never heard of the brand before.
The end result was that I now see the night and day difference between headphones whose tuning makes them perfect for gaming, the PC360, 558, and the K550. And the headphones whose tuning makes them pretty good for gaming but more fun for general listening, like the Momentum and the Denon D600. From what I've read, I'd put the X1's in the latter category. Although I am aware that many people think that the X1's are very unique for an open full size headphone.
If I had the money, I'd probably get the PC360 just for gaming, as it's slightly more than the 558, slightly less than the Q701 plus mic, and is a complete and competent headset ready to go. Then I'd get the X1's for listening to my collection of Digital Audio Tapes and general listening. I may do just that in the future when my tax return comes in, but for now I need to focus on just one, so I'm leaning toward the X1's as they can server both purposes very well with a mic and are at a very nice price point.
Well, I happen to own both the X1 and HD558 currently.
I can tell you that after a month of using the X1 and HD558 previously, switching back and forth... I have the HD558 back in my box and stashed safely in my cupboard. Why? Because I don't seem to feel or hear the fact that the X1 has any less of a soundstage than the HD558. They are in fact comparable and in some cases, the X1 is airier with better depth. Not to mention the fact that I don't have to deal with almost no-bass on the HD558 anymore, it's a bliss to have the X1.
Now, I do own the HD558 for more than 8 months prior to owning the X1 and it has been my main headphones most of the time. So to switch to the X1 and get all of what the HD558 had to offer and more, that's saying something. Perhaps the only advantage the HD558 has is the more forward mids and peakier highs, both of which would be a better fit for metal or fast music. It isn't by much by the way.