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.
Thanks for all the posts, very interesting. My amp is a 15 year old Yamaha RX-485, I'm also running a 15 year old Yamaha CDP. I cannot decide if I want to upgrade the speakers or the electronics! Budget is about $1600.
No one has mentioned anything about high-passing the B&Ws, would that help? I'm afraid it would hurt the imaging of the sound, too much coming from the sub in the corner.
Even if I upgrade the speakers, I will still be missing that extra low-end oomph; I think I need a sub woofer.
I will probably purchase a <$1000 integrated and mate it with a sub woofer. The room is small, like 14x12x8. Possible combos include Cambridge Audio 650 + SVS PB10, or an NAD C326 with a Velodyne DEQ-10R. NAD to sub connections are quirky. The CA has A/B switching, so I can do a high-level connect to the sub.
If you're getting a powered sub, then it does not matter whatsoever whether your bookshelves go down to 42Hz or 49Hz. More important is how the speakers perform to your liking, in any case.

As for the high frequencies, it's really irrelevant whether a speaker goes up to 22kHz or 30kHz since human hearing maxes out at 20kHz, and for most individuals, much lower. So unless you're playing SACDs of dog whistles for your pet's enjoyment, this is also a non-issue.

Get the MAs if you like them better than the 685s, but not because how high and low you think they can reach, especially in this case.
The MA BR line is their entry line and IMO inferior to the B&W 685s you arleady own. If you like the MA sound, I would consider the new MA RX2. These have an 8 inch woofer in a bookshelf cabinet and they rock. Really high value for money. Also, they would be fanstastic with a NAD C326. The Cambridge stuff will probably be too bright with MA speakers. NAD is a much better choice.
Jaxwired your point is well taken regarding the BR2s, and if I had done my homework before buying the B&Ws I may well have ended up with the MA RX2s.
I think I am going to buy the powered sub and upgrade my amp as well; with a powered sub, would the CA still seem as bright? I like the CA's dual speaker channels, enables me to purchase new speakers (B&W 683 or better) later and basically have a 4.1 system, on my way to building the perfect 5.1 surround system for the living room.
Also, the CA 650 has 25 more watts than the NAD, but it does not have main-amp-in connections. Still no one has posted regarding the idea of high-passing the 685s - good idea or not?
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