Originally Posted by Biscuitz
However, overall, the HD650 is an altogether more natural sounding headphone to my ears, with seductive vocals, greater transparency, and greater detail - in fact, because I felt the HD650 sounded more detailed than the X1, in my A/B sessions, I actually heard a slight "veil" when listening to the X1!
Yikes, maybe I shouldn't have said that! It's one thing to say a headphone is veiled sounding. It's another thing to say a headphone sounds veiled when directly compared to another headphone. That's the case here - the X1 doesn't have a veiled sound. But when you compare one headphone to another headphone with greater clarity and detail, then the sensation you get is of a slightly more veiled sound on the less clear headphone.
As for the O2, I can't say I've heard it. But just remember that a lot of inexpensive headphone amps can "power" virtually any headphone on the market. "Power" in the sense that you will get plenty of volume. But, as many will testify here on Head-Fi, amping is not just about getting volume. Having a better, more powerful amp is about achieving greater dynamics, clarity, soundstage, detail retrieval, bass control, etc.
In my experience, not a lot of headphones really benefit significantly from better amping. The HD650 is one of the few headphones that I've heard on a couple different setups that I feel improves slightly with better amping. To me, the difference between an HD650 amped by a decent budget amp (O2) and a powerhouse of an amp (Lyr) is the sense of dynamics gained by the extra power. The HD650 is a soft sounding headphone on my current amp. On the Lyr, it's a dynamic powerhouse with bass slam to please. Keep in mind, the general sound signature remains the same, but specifically the impact and tactility of the bass is quite another beast. Another headphone I've actually heard quite a substantially difference with in amping is the HE-5LE - I've heard this on the Schiit Magni, which is like the O2. It has plenty of power to provide all the volume you'll ever need on the HE-5LE. But after hearing the HE-5LE on a $219 speaker amplifier, it was really a different beast. NOTICEABLY better in regard to soundstage, separation, clarity, bass control and bass slam.
First things first, find out which headphone you like - then mess around with amps if needed. Grizzly, you did the best thing you could do, realistically. Grab both headphones and compare them for yourself. You may be surprised by which you prefer. I often am surprised after reading a lot about a headphone and then trying it out - e.g. the HE-400, didn't like, and e.g. the Denon D2000 I loved, which I really didn't expect to. Btw, my D2000 gets more headtime than my HD650 ;)