I bloody hate the HD700's tuning but the driver it's self is technically good. I think the HD650 is on par with with it from a technical standpoint but it has a more natural sound so I think you'd like them if you like a smoother response.
I don't think the LCD-2 are really an upgrade over the HD650 apart from bass texture, extension and impact. If you want something a bit cheaper (£499) I really love my Nighthawks. They remind me a bit like the old Denon D7000 but improved in all areas with a more natural sound to them.
The reason I like them so much is because they are different from all the headphones out there. Some people hate them, because they are scared of different. They can sound overly warm on unresolving equipment, but have a good tonal balance with some of the best bass you will find. I think the are about on par with the LCD-2 but just different, nothing sounds like the Nighthawk.
Having owned the Nighthawk twice, the second time I was a bit worried about having it as my one and only..because it doesn't really boost anything so it can sound a little less exciting compared to something like the Fostex TH900 - but man! these are fun in their own right. When I devoted time to it, it sounds fairly natural, it's when you start comparing the Nighthawk to other headphones when it makes you think is this really what I want because of Skylar Grays refusal to tune them like the rest which all pretty much have a boosted something up top.
Sometimes the vocals can sound a little distant compared to the HD650 but my god, the tonality of the NH is really stunning! liquid, smooth, effortless, golden is what I'd describe the sound as, they will keep me going until a HD650 successor.
Problem with Audeze is the QC is awful, things like rattling drivers, failings are a bit too common, it's a shame because they sound great! You could also try some of the T50RP mods like the Alpha Dogs, ZMF, Paradox etc - These are closed so keep that in mind.
