Not every headphone is reference-class, and I don't expect reference-class performance from a product like the AH-D1100 which is priced and designed for casual listening. There are a different set of concerns, and I'll try to judge the D1100 accordingly.
 
Denon has cleared the baseline here:
 

1. the jack is designed with a recessed flange so it plugs into in all but the most overbuilt smartphone case.
2. the headphones are light and comfortable to wear
3. they look good
4. the closed back design offers good isolation
5. the headphones are easy to drive and sound good without needing a dedicated headphone amplifier
6. the overall sound is clear and and full-sounding, without excessive coloration

 
There are downsides however,
 

1. the oval earcups press a bit too firmly into your neck under the ear, reducing overall comfort
2. the neodynium drivers suffer from the microphonics typical of the material
3. there is an excessive mid-band boost around 80-100 Hz 

 
It's a shame about the bass boost. I'm not against the idea of a bit of a lift on this class of headphone, but it is overdone here to the point of being distracting.
 
Final word about price. Retail in Japan as of this writing is 6500 yen, new, and I picked up a set used for about $40. For $75 or so I'd say they are nicely made headphones. At double that price the relatively flimsy build would come in for more serious critique. I understand and appreciate that Denon were going for rigidity and lightness here, but they feel cheap nonetheless.

Let me just say one thing up front: if you have any complaints about the speed or the bass extension of these headphones, you need a better headphone amp. /endofdiscussion The HD600s will take the best in source material and amplification, and give you the best sound in return. It's not coincidental that these cans are held up as the reference's reference: more than any other headphone I can think of they sound like whatever it is you are listening to. Their most notable audio characteristic is this ... amiable compatibility. That and the ability to play cleanly at very loud peak levels. Combined, the HD600s are ready for whatever you care to throw at them, never drawing unwanted attention to themselves, always sounding great.
 
Perhaps part of the secret to this neutrality and high enjoyment factor is the way they dial down the resolution just a tad. A fraction de-focused, one notch less treble intensity - blending the music into a coherent experience rather than individual strands of detail. Some people might disapprove, I call it genius.
 
These are comfortable, durable headphones built to a high standard. The foam pads on the earcups and headband died after a decade or so, but I easily replaced them with the new parts from Sennheiser.

This is a great sound card, full featured for gamers, home recording, and home theater, as well as traditional high-end audio.
 
I am only interested in it as a source for high-end audio (2 channel) and my review only considers this one aspect of its functionality.
 
Notes in passing,
 
1. Drivers install without a hitch on Win 8.1(64 bit) and seem stable, so hopefully Creative has put that history behind them.
2. A lot of DSP "enhancements" are turned on by default. For the best sound, turn them all (equalizer, AEX, 3D, "crystallizer", etc) off.
3. The card is physically quite similar to the SE-200PCI, but there is now a separate plate for the multichannel analog outputs, replacing the breakout cable. So the full setup will take up two slots in your case, though the second is optional.
4. 120 dB is better than the SE-200PCI, and it is less susceptible to noise pickup too. (I suppose due to the full metal shielding over all the analog sections.)
5. As most people note, there is a built in headphone amp (good!), but no header for routing audio to the case front panel (not so good!) so overall the headphone jack is a pain to use. I use the line out RCA to my headphone amp, so its not an issue for me.
 
Once set up, its all nicely integrated with Windows (line out volume is set in the Windows mixer), and you can pretty much forget about it.
 
The sound is (once you get rid of the DSP, see above) smooth and detailed, with superb spacial resolution. Overall neutral, tonally refined. No digital glare, no artificial warmth or emphasis. Some people might find it too restrained. Not everyone wants or needs this kind of performance in a computer sound card, as you need similarly excellent system to appreciate it.
 
So that brings us to the price. Let me just say that the $400+ sticker price on this in the US is just insane. I got mine used, so back in "comparable to the SE-200PCI LTD" territory. It's $300ish retail in Japan, which is 50% more than the SE-200PCI LTD ever sold for, but justifiable, perhaps. Either way I can't bring myself to recommend a sound card that costs that much, and that much more than you can get the 200PCI for. Especially as 80% of people are probably going to prefer how the 200PCI sounds anyway. And given the 200PCI sounds wonderful, why take the risk on the '300? For 2 channel audio the numbers don't add up.
 
http://www.jp.onkyo.com/pcaudio/pciedigitalaudioboard/se300pcie/gallery.htm