So I've been testing out this m903 with some different headphones for the last few days. I wanted to share my results with you guys since you all helped me when I needed information.
First of all, the m903 is sick. The conversion is stellar and the feature set is unbeatable for a DAC. If you have studio monitors also, I highly suggest this box.
Now to the headphones....
LCD-2 (Rating 9.5 out of 10):
Sound: Incredible. Natural. Deep. Impactful. Detailed. Warm. Punchy. Wide, but controlled.
Comfort: Heavy, but still easy to wear.
Build Quality: Really sturdy, although the cable connection points stick out a bit far and could break with a bit of leverage, but would take quite a bit of it.
Misc: Came with a very useful hard travel case.
HD800 (Rating 4 out of 10):
Sound: Shrill. Painful. Seriously weak bass. I do not see the appeal at all. Not only was it not incredible, but it was honestly bad. As soon as I put them on my ears began to hurt even though they were at approximately the same level as the LCD-2's. The highs are brittle like a chalkboard. I suspect that anyone who thinks that this combo has a great high-end has been listening too loudly for their whole lives and probably has some hearing loss (natural hearing loss usually occurs in the higher frequencies). I've had my hearing tested recently and my loss is near the average natural loss for my age (25), so I don't think it's my own problem. They sounded a little bit better with my Apogee Duet 2, but I only suspect because the Duet is not as revealing as the Grace - and even then, still painful in the Duet. What are you people smoking who like these things? I would liken it to a regular TV that has the brightness turned all the way up and then marketed as "HD". These are absolutely a worse listening experience than even my AKG k702s.
Comfort: Lightweight, comfortable ear pads, although the band is a tad big.
Build Quality: Crap. Plasticy. Feels cheap. Exposed speaker cone that can be easily damaged. The only upside to the crap materials is that it's light, but it's almost so light that it feels like it's going to fall off of my head.
Misc: Doesn't come with any useful accessories.
BeyerDynamic T5P (Rating 7.5 out of 10):
Sound: Rich, balanced, great tone. The only that really separates these from the great quality sound of something like a LCD-2 is the "closed" feeling to the sound. But, that's what you get when you wear closed-back headphones. If you need to have very minimal sound leakage to the area around you, then I would definitely recommend these headphones. Otherwise, get an open pair. I don't even find the open cans are really all that loud at normal listening volumes, although they can be like small desktop speakers when cranked all the way up.
Comfort: Good. No complaints. Not amazingly luxurious, but good.
Build Quality: Solid. They feel firm. Nothing is going to break.
Misc: They are powered well from anywhere....the m903, the Duet, my laptop, my phone, etc. It doesn't really affect them too much. They also come with a nice protective box and an extension cable.
(I will receive the LCD-3 today and will write here again with what I think of them).