Personally the P5 aren't anything special if the looks and isolation don't do anything for you - especially for $350. Compared to the AE2 you'll give up soundstage, detabably give up isolation and comfort, and probably a little extension. The AE2 are a good all-around headphone owing to their fairly smooth and rolled-down top-end - they play nice with everything. If you want to upgrade from them you have a number of options depending on budget and preference - but you'll have to be somewhat more specific as far as what you want.
As far as "Quincy Jones made a headphone" - I'm not sure how to respond to that. Quincy Jones has licenced his name out for a number of AKG products that've been re-branded as "Quincy Jones Edition" headphones; the Q701 is the "top" of that range, and is derived from the K701. Very different sound from the AE2, and they're not suitable for mobile use - really depends on what you would (or wouldn't) change from the AE2 as to whether or not they'd be a good fit. If you're looking for a bassy headphone, they probably won't deliver though.
Personally if I had to pick a "luxury" headphone (like the P5), I would (and did) pick the Audio-Technica ATH-ESW9; better mids, better fit, I just like what they do with the music better (and they cost less). Less isolation and more fragile though, but I don't use them for mobile applications - life is good. However if you're talking about comparing either of those to the 701, that's another story altogether - the 701 have a much larger soundstage; flatter, dryer, and more analytic overall sound; and different fit (they're around-ear, and open). It makes them a different beast altogether - personally I like them, but I think there are better options as "forks" from the 701 (the 701 are a really good entry into high-end, and do a little bit of everything relatively well, but master nothing) - if you want a faster headphone, a more lively headphone, a better staging headphone, etc there are options. But that comes down more to preference than anything else.
Overall I think the AE2 are a good candidate for the all-around kind of use you're after, but there certainly are headphones that would represent an improvement in one way or another. I don't think the P5 would be that headphone though - the ESW9 would be a better choice there imho, or the AE2's bigger brother, the QC15. Otherwise from that, the K701 aren't a bad choice, but you'll give up some bass impact; there's also some JDM imports I'm partial to suggest, and depending on how much you feel like spending, some American exotics.
