I was in sort of the same boat, I went with 700x35 Specialized Nimbus...they have worked well so far.

IMHO a hybrid (I have a Trek 7200 myself) is not very "Aero" to begin with, tire width does come into aerodynamics but is probably not a huge factor for most riders :-). If your existing tubes are OK you might be able to use them in 700x35 tires, but would probably need new tubes if you went much smaller ??

I have thought about narrower tires than 35 but it might snow before I can wear the 35's out this year :-).

Bill