I would say so. I came from HD598(minor upgraded from HD595) and the change is dramatic. It is basically a straight upgrade from HD598 IMO in every regards, most notably in the soundstage and the detailing area. I listen to classical and jazz (mostly instrumental with HD700) FYI. Although I won't recommend these for listening to pop or similar genre as the treble will be too prominent and bass isn't that great. Also, HD700 and HD800 are pretty sensitive to bad recording and source, keep that in mind.
I, in general, like my sound to be on the slightly warmer side of neutral, so I tend to like a very natural sound, with a touch of warmth (though I prefer a completely neutral/analytic sound over a bloated or thin sound). For example, my TT is very neutral, and paired with a Emotiva Phono-PreAmp (very neutral), I tend to enjoy it very well with my Momentums, because they are warmer, so they compliment each other. I have other sources that are quite warm, and find the Momentums to sound bloated, but just right with Amperiors and HD700; the HD650 sound good with everything.
The HD650, compared to the HD700 are warmer, and laid back (but never bloated, never messy). So because I do feel that the HD650s always sounds good (though a bit warmer), its hard to tell if you like a warmer sound or more neutral sound. Would you say the Asus is warmer? I would think a DAC/Amp that's 'perfect' for the HD650 would be something that is very neutral (since my preference is a sound just a tad north of warm); to achieve this with the HD700, I'd prefer a warmer source/amp.
I do agree that the HD700s are much less forgiving with poor recordings, to an extent. If the sound is very grainy, or has very specific treble peaks (5-7Khz), then the HD700 are unforgiving, but I do think they can really bring out some nice detail and controlled sound out recordings whose problems are NOT with very specific treble peaks. I listen to a lot of Jazz, but also to a lot of Blues, Hard Rock, Metal, Electronic, Rap, etc...I basically listen to everything and I think the HD700 are great with many typed of genres, even the bassier stuff like rap and EDM. How versatile the HD700 will depend on how good your recordings are and the amp and DAC. It will never be a bass monster, so if you NEED your rap to bass with authority, and you want a step up from a 595/598 then I would go with the HD650. However, you'd be surprised at how satisfying the bass could be on a 700: it will be very detail and very controlled, you will actually hear the bass strings resonate on a good recording (like Snoop Dogg's Doggystyle on 48/24 DualDisc).
The bass will have more impact and be much more detailed than the HD598s. I think for people who have owned more bassy headphones (like the HD650. Momentums, Beats, etc), will probably find the bass of the 700 a lil off-putting at first (it was for me at the beginning, but I grew to appreciate the different experience in a matter of about 2 weeks, with the better amp and DAC), but going from a HD598 or similar can to the 700, you will probably like the 700s right off the bat.
I agree with SNSDLuv, the improvement over the HD598 should be dramatic. The difference between the HD650 and HD700 in terms of detail is very noticeable, and the difference in soundstage is downright amazing (amazing because the HD650 has a great soundstage). I think the HD700 are THE natural upgrade to the 595/598s. If you like the sound signature of those cans, they HD700 will be everything they are, but just better at everything. The change between the HD650 and HD700 is not quite as natural as they do have a very different sound signature: there are still some specific songs that I still prefer the HD650 over the HD700, but overall, I am very happy with the HD700. Its a great compliment to the HD650, and a natural upgrade to the HD598/595.
Are they worth it? Not at $1000. At $650 (or less), yes, yes they are worth it!