What type of cables are you using? this could be your problem.
Do you know if they were broken in well? I had the 7bs and now have other Aerials. These speakers take quite some time to come into their own. When I first received them I wanted a refund. It took at least 100 hours before they sounded good. I really enjoy Aerial so I can't imagine them leaving you disappointed.
I asked them about the speakers being broken in. The response -- they had been used as demos for the past 12 months. That in itself does not guarantee being broken in, but the likelihood is high.
I also checked on the amps -- they were quite warm, so that was not a problem either. Again, like I said -- the same system sounded much better balanced with B&W Nautilus 802, which are not exactly known for their warmth. I just do not know what was wrong -- previous experiences with Aerial speakers (10t, 8b) was exactly the opposite.
Something is definitely wrong - sort of. Your impression of the B & W speakers is very accurate; smooth, musical, "sweet", though to my ears not imaging champions and a bit fluffy down low. However, I have never heard Aerial speakers sound like you have described them. They are extremely tight and articulate down low and image like crazy. BUT, they need to be in EXACTLY the right spot in a room, or they simply don't work. Cable and system synergy issues aside, this is most likely the root of the problem. The 7B is a worthy speaker and very solid competition for the 804; between the two it basically boils down your taste in music and what pleases your ear.
I have found very few speakers can match B&W wide dispersion and pinpoint imaging. Only narrow baffle speaker like Audio Physic Virgo 3 were in the same ballpark. Maybe the distance between speakers. Try 8 feet or more apart and sit 8-9 feet away.
Aerial could be CDP - or amp not having enough power to produce bass. That could be the lean perception because the $3,500 Aerials I heard were warmer, richer, less detailed than B&W.