What you want to do is the best way to have one setup for video and high quality 2 channel audio.
Here's a lot of yap about it for you and others thinking about doing this.
I see the AVR has a full set of pre-outs, you probably know you need front pre-out to use a separate amp for the front speakers.
and you probably know you need HT Bypass INPUT on the 'front stereo system' you will use. I learned about it late in this threadhttps://forum.audiogon.com/discussions/avr-internal-2-channel-audio-mode-or-ht-bypass-external-equip...
That let's your AVR control the front volume along with the center and surround speaker's volume when using it for video.
You will need to make pre-adjustments in each speaker's level in the AVR's menu to get them working together (adjust's all the avr's individual channel pre-amp's for each speaker's efficiency). Then every thing goes up/dn together from that base 'matched levels'.
Once you get what you like, write those settings down, if for any reason you need to re-set, you will need to do it again.
Meanwhile, for Audio only, the front system will be a 2 channel Stereo Music System for Audio only.
You don't want that driving the center channel, I have not seen HT Bypass that allows front and center, has anyone?
Speakers; my experiences
How much bass?
Of course you want the bass when listening to front 2 channel only, (if thru the AVR, when the AVR is OFF, the sub(s) are off).
Your B&W 902's make enough bass for you I expect.
For other's thinking about this:
The front speakers need to either produce the bass, or the two channel system needs to send the low bass to the subs via a crossover (separate or built-in the sub(s).
Then the subs are always on for video or audio.This removes the bass load from the front stereo's job, thus is the best way to use a lower powered front amp.
IF the front amp does not have pre-out/main in, you can use the front system's speaker wires, go to sub, then everything except low bass passes to the mains. That adds the bass, gives the smaller front mains a break from trying to make bass they cannot do, but the front system is amplifying all frequencies.
Center channel speaker:
Physical considerations are paramount as well as sound quality. My experience: directly below the TV for proper imaging, so it depends how much height, then how much width you have.
If TV is not wall mounted, the base/legs of the TV are critical for center speaker location. Downstairs, center stand, I had matching wood, so I was able to build a 7" riser to fit on my cabinet: both to get the TV at proper viewing height (we used stacks of books to find the best compromise for us, I'm 6ft tall, Donna's 5 feet tall (if the sun warms her up).
And to allow the sub to fit under any TV I put on top of the riser's top glass shelf. Upstairs, I purposely picked a TV with legs at the far ends, left room for cable box and dvd player between the legs.
Then, sound quality, efficiency, looks to go with the front speakers. I avoided rear ports,
had the little Bose for many years, blended wellhttps://www.bhphotovideo.com/c/product/291864-REG/Bose_19158_VCS_10_Center_Channel_Speaker.html?gcli...
recently changed to this Klipsch (no rear ports)https://www.klipsch.com/products/r-34c-center-speaker
fits under the riser shelf, looks terrific, we use it with the grille off. It is far more efficient (96db) than my front mains, I had to cut the center channel a good bit to match levels. It blends very nicely.
Rear surrounds (I only do 5.1 surround): I have always simply used small speakers, laying on their back, shooting up using the space between the back of the sofa and the wall 5" behind as a kind of horn. I had small energys, then some paradigms, now a pair of Klipsch (rear ports stuffed).