I really do enjoy my P7s connected right out of my iDevices. They did not sound nearly as good when plugged into my laptop headset out jack; but, that was before burn-in and I did not try it since. The same lossless format songs sounded much better through my iPad or iPhone even before burn-in. I advise going to an Apple store and trying them out.
While I am a long term fan of B&O HiFi, I will say that the B&W P7s are really nice. They also sound better after burn-in. So the demo units at Apple will likely give you a good representation of the P7, as I believe the music plays through them all the time the store is open. You can also demo them at Best BUY, some locations.
I also thoroughly enjoy the Sennheiser HD598, a bargain around $150 at some FRY's electronics stores.