Instead of asking us to tell you what headphone to buy, you should be asking for information. That way, you can buy the headphone you want. Also understand that no headphone is perfect. The three headphones you listed are all a lot better than anything hanging from a hook in a Walmart, but they're not the top. You're not going to buy the ultimate headphone for a few hundred dollars. There's really no clear winner among headphones that cost over a thousand dollars. If you ask people what to buy, they'll tell you what they like.
The HD650 is a Sennheiser. Until last year, it was Sennheiser's flagship, but it was also a disputed flagship since there were many who preferred Sennheiser's old flagship, the HD600. In a nutshell, Sennheiser's house sound tends toward the laid back. Sennheisers are not snappy headphones with a lot of "coloration." To compare this to a "glass half full" debate, are you the kind of person who walks up to a receiver/amplifier and turns the bass up or down? If you're the "bass up" type, it's probably because you like to spice things up. If you're the "bass down" type, it's because you prefer a more neutral presentation.
Sennheisers cater to the neutrality crowd. The $1,400 HD800 is touted as "the best headphone out there" by listeners who, above all, want accuracy. While there's plenty of variety among Sennheiser cans, the house sound tends toward balance, neutrality and accuracy - even if it makes for a more boring presentation. Sennheisers are valued most by purists and musicians who don't want the music altered in any way. They don't want the music to sound "good"; they want it to sound "right." The HD650 was introduced to quell criticisms that the HD600 didn't have enough bass. The HD650 has more bass but less treble, particularly after 10 kHz. This produced a split in the New Coke/Coke Classic split in the Sennheiser community (not unlike the Grado split between the RS1 crowd and the GS1000 crowd). Sennheiser's fix, like Grado's, was to introduce a new high-end can that "splits the difference." Both the 600 and 650 have more mid presence than the 800, but the 800 has a bass signature that's closer to the 650 and a treble signature that's closer to the 600).
The nice thing about the introduction of the 800 is that it has depreciated the cost of the 600 and 650, so you can take advantage of the savings. If you want more bass, the 650 provides it. If you want more sparke (for a Sennheiser), the 600 is still there.
Of course, if sparkle is what you want, the K701/702 provides it in droves. While the HD650 has a decent soundstage, the K701/702 provides an even wider one, with tremendous sparkle that's more engaging than the Sennheiser line. On the other hand, you really have to use your amp to get decent bass out of it. With a Lisa III, you should be fine in that regard. The HD650 will give you more bass but the K702 will give you more soundstage and more treble energy (It's not laid back). Without an amp, you'd be better off with the HD650, but with a decent amp, the K702 offers you a solid alternative. As I've owned both, which I liked very much, I call tell you that I ended up selling the HD650 first, just because I'm not as big a fan of the laid back approach. I need my bass, too, but I like sparkle, more sparkle than I was getting from the HD650. Big fans of the 650 hawk upgrade cables, particularly those with silver, to brighten up the HD650 - but that's an expensive proposition. If this is a one-time shot, you'd be well-advised to take into account that the HD650 is darker than the K701. I'm not saying it's a "dark" can but it's going to be more neutral, more laid back, than the K701.
Which brings us to the beyerdynamic. The DT990 has the most bass of all three headphones - and the most treble. It is not a flat headphone. It is not a laid back can. It's not neutral. It's a party can extraordinaire. It has throbbing bass and the most pronounced 8-10 kHz treble spike. If you're looking for neutrality, you'd want the HD650 but if you want lots of bass and lots of sparkle, the DT990 is a no-brainer.
If you're asking me to do the thinking for you BUY THE FREAKING DT990.
