So, I got my headphones in last Friday and have put a ton of hours on them in the past week. I have used them through my Titanium HD on my computer amped and unamped, for music and gaming. I have used them amped and unamped with my iPod and HP Touchpad, unamped through a friends iPhone 4, and unamped through my work laptop.
First off, the Touchpad and iPhone didn't get the volume very high, but my 5th Gen iPod, work laptop, and Titanium HD had no problems powering the headphones unamped. With that said though...adding the amp to the iPod really made the headphones come alive and I don't think I will ever use them again without the amp. Gen. 5 iPod->12V cMoy->DT770 Pro/250 is how I intend to use these headphones on a daily basis.
To answer a previous question....they sound incredible through the Creative Titanium HD unamped. I have listened to it plugged straight into the headphone jack and also with an RCA-to-3.5mm jack plugged into the RCA line out ports. Both drove the headphones comparably, but I liked the sound better out of the RCA line-outs (I heard it uses an extra op-amp that the headphone jack doesn't use) and will probably only use that from here on out. Just to give an idea of how well the Titanium HD powered these headphones....headphones plugged into RCA adapter plugged into the line-out ports and Winamp set at 100% volume....45-50% Volume in the Creative control panel is what I would consider comfortably loud and it can definitely be turned up to ear damaging levels.
Also, I like these SOOO much more than my AD700's for gaming. The sound stage and situational awareness is what I love about the AD700's...and while the DT770's don't have quite as much of either, they aren't very far off and everything just sounds better to my ears through the DT770's. Actually having bass and good situational awareness at the same time is a very nice thing. At this point, I am considering getting rid of my AD700's to get another pair of DT770's to use at home on the computer and to watch TV with while my girlfriend is sleeping.
As far as the headphones go for music (the main reason I got them)...they are great. I was really worried for a little that there would be too much bass (a common opinion of the 80 Ohm DT-770 Pro), but these are just extremely balanced to my ears. The bass is there, but not overpowering. I honestly believe my friends M50's have more bass than my DT-770's....but the bass from the DT-770's seems to be of slightly higher quality and can plays the super low frequencies better. The mids don't seem to be nearly as recessed as I expected from some of the reviews I read (but they are still a bit recessed)...and the treble isn't harsh at all.
The isolation is good, but not as good as my buddy's M50's are. They seem to block outside noise well, but have more sound bleed than I expected (probably due to the small port hole on each hear). I can still listen to them at work at loud enough volumes to make me happy and not bother others, but I do feel like there is a fine line between no sound bleed and very audible sound bleed. I am constantly pulling them off my head to see if you can hear anything on the outside...I'm sure that will pass when I get more used to them.
These headphones are extremely comfortable...I love both the ear pads and the headband padding. They do clamp more than I expected, but no where near as hard as the M50's (which is really the only reason I didn't just get M50's to begin with). I'm happy wearing them for many hours straight. Just for comparison sake, it's like Goldilocks...M50's clamp tight (too tight for me), AD700's are very loose (nice if you don't move your head at all), and the DT770's are just right.
I only had one small issue (that scared the crap out of me)..when I first plugged them in, the right speaker didn't work at all. I tried it amped and unamped on multiple sources and got nothing. I thought "maybe it is just stuck from tight tolerances and will work itself free." Luckily, I was right and after about 15 minutes of music out of my computer, it finally started working. It honestly had me worried for a minute though.
Overall, I absolutely love these things.