frequency response - B&W vs. Monitor Audio


I currently have a pair of B&W 685s and I am considering replacing them with a pair of Monitor Audio BR2s. The MAs freq resp gets down to 42Hz; the B&Ws only get down to 49Hz. Is this an audible difference? I would be getting the MAs through a friend who has access to wholesale prices and I will not be able to audition the MAs.
2nd issue - I am considering high-passing my bookshelfs through an active crossover in a powered sub. This will cut out frequencies below 80Hz before the signal gets to the amp and the bookshelfs. If I do this, does it matter if I upgrade to the MAs? Their high end is 30kHz, the B&Ws high end is only 22kHz. Thanks.
realremo
Bob_Reynolds, thanks again for another interesting equipment suggestion, will research it in the near future. Regarding surround sound, I won't be able to place a system in the living room for about a decade - kids are too young. So I was thinking about starting to build up the speakers - B&W 600 series looks very nice.
I am going to stick with the 685s and definitely get a powered sub. Amp is TBD.
Thanks all...
THREAD UPDATE:
I have all new electronics in the listening room, and I am currently "borrowing" the 685s from my upstairs home theater. I want the 685s back up there, so I am now considering Monitor Audio BX5s, PSB T45-T55...listening room now features a newer Denon changer, the Halo P3, and a 200wpc Rotel amp...