The Q701 soundstage does improve slightly with an extra amp, but I would only expect this from a decent desktop amp. I don't remember any improvements with the E9 even, and I checked it a few times, but when I hooked up the M-stage I had to do a double take to check the sound as it was a bit airier and wider sounding. Don't expect the Q701, or just about any headphone for that matter, to reach AD700 size soundstage. AD700 has the largest soundstage I've ever heard (you can check my profile for what I've heard), but its got some serious balance issues.
On the flip side, I wouldn't expect the AD700 to even come close to the Q701 on bass and overall signature balance. You can boost it, yes, but it will never have the
body and impact from headphones like the Q701 - which keep in mind has only a mild mid-bass hump. Believe me, I've tried boosting the AD700 bass, and it definitely helps, but it still sounds a bit artificial and the quality and texture of the bass gets pretty homogenous after boosting. The AD700's bass starts to all sound the same and comes from the same spot in the soundstage.
For me, the balance and naturalness of the Q701 is
definitely worth the price difference. The AD700 is great at what it does, but its weaknesses really show when you put against some fuller sounding headphones. The treble sounds sibilant and grainy and the bass is sad
. The Q701 was what made me finally sell my AD700s, as I finally found something that had the best compromise I'd heard between soundstage and signature, to my ears. I just don't think there's much out there that will keep the
"AD700 staging but with some ~60Hz bass capabilities for under $200." You will have to lose
some soundstage.
[Evshrug: that's basically what I said to the other guy] Honestly, I think the Q701 is the best bet for what you said your looking for - and it's what I would've recommend if you didn't already have it. If the Q701 isn't doing it for you, the soundstages only get smaller from there. The HD5xx are pretty darn large, and they also have more bass than the AD700 (less than the Q701 though). Still smaller stage than the AD700. The Beyer's I think are
slightly smaller than HD5xx and Q701. The Q701 is just about the same size as the DT990, maybe slightly larger - but I prefer the positioning on the Q701.
Also, the jump from the Recon's THX to Dolby Headphone may be a better investment. I can't really say as I haven't heard it, but MLE and Nameless are favoring the mixamp.
You could keep your eye on the AD700x and what not, but I'd be surprised if they're a huge improvement in bass over the current AD700. They look even more open, and I think improvements in bass will come from the new pads sealing a bit more.