The regular over ear Momentums (but also the on ears, since they are similar). I actually dont own or have heard the Senn's you listed, but I found the Momentums to be much more bass heavy than any of the Senns I own (HD429/HD449/PX360/Amperior/HD650/HD700), which is what I wanted from them. Although the HD650 and Amperiors have good bass, with the Amps having the harder hitting and the HD650 the smoother more controlled bass, I found the bass on Momentums more sloppy, sometimes affecting the lower mids. So I felt they were a bit different from the Sennheiser sound of the other cans I own.
As far as treble peaks go, both do have a bit of harshness right arround 6-7kHz, it just seemed a bit more pronounced on the HD700. I don't know if that's because the HD700 does a better job of giving more detail, and seperation, it just seems more noticeable on the HD700; its like I notice the treble peaks on both, but it just bugs me more on the HD700.
Other than that, I love the HD700s: if price was no object, they are easily my best headphone, while the Amperiors are third (second being HD650). Those positions switch if I factor in cost (especially cost of needed/recommended equipment): I paide $350 for the HD650, $220 for the Amperior and $650 for the HD700. The HD700 is a great headphone, but its not twice as good as the HD650, more like 25% better.
Plus, to tame some of that treble peak,I feel like you need a good amp and dac (I got the Schiit Asgard2 and Bifrost, an additional $670). With a good amp/DAC, the HD700 starts to pull away from the HD650 (the HD650 just needs an amp with a lot of power, and E9 did me fine for over 2 years). The Amperiors are pretty much game out of the box, with no additional equipment needed, any DAP, Laptop, phone, headphone out would work just fine. They also sound damn good, and I think they sound miles ahead of the Momentums which cost me $300.
You think Amperior is "miles ahead"? Hahaha, Now I'm not sure I want to bother trying the over-ear Momentum.
Actually, what I meant by the Momentum on-ear not sounding all that different is that the tonal color of the mids, treble, and bass as well as the very bass character are all terribly similar to the headphones that I listed. Some of us suspect that PX360 = HD360 (although the HeadRoom graph makes me think twice), then HD380 is basically an HD360/PX360 with stronger, peakier treble, more transparency, a pinch tighter overall, and mildly stronger low bass boost. All, even the Momentum I've got, boast bass that is rather "wooly" sounding to some degree or another. HD280 has the best balance of all the closed Senns, but is otherwise a mild downgrade overall from HD360 and HD380. The on-ear Momentum is an upgrade in sound over all of the closed Senns except HD380, although I am not fully certain on that because I no longer own an HD380 to compare with. The on-ear even smokes HD25/Amperior, but it offers almost no isolation at all.
HD700 will be a piece of cake for my pimped out Dynalo.
Edited by Mad Max - 3/2/14 at 3:52pm