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
The 'demo' disc that came with my sub has an organ track with a 16 2/3 hz pedal tone.
The Saint-Saens Symphony #3 with Organ is awesome.
It'll rattle everything in house. You can see the warble in window reflections.

I believe the Bosendorf Imperial Grand goes 1 octave below A1. This instrument has 97 keys, not 88.

Careful!
Magfan you are indeed correct, the Bosendorfer mental amount of $$$ Imperial (best piano on the world by a long stretch)goes down to C (additional 9 notes) to give a full 8 octaves, so A below A1 (if there was one) would have a Hz of 13.75 add a few (can't remember the multiplyer to give a semi-tone increase (been a long time since I was at musical instrument technology college), and it is still
rather lowdown Hz wise.I've only ever played on the Bosendorfer 7'+? model daily (way back), what an instrument that was! Having only tuned piano's (back in the day also) with the Standard A1 27.5hz(that is/was hard enough to do) the big fella must be a piano tuners nightmare all those additional notes in the bass, if you have a cold, forget it pack up your tuning crank, go home, you ain't gonna hear the 'beats' that low.
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.