B&W 800D2 - Bi-amping vs Bi-wiring

Or am i better off buying a pair of CA-M600 for each speaker?

Do you mean four CA-M600's? I'm thinking no, as that would not be necessary. I do agree that you would benefit from having more power. Adding another CA-2200 will achieve this, and as Zd542 said, the vertical configuration will be best, however, a pair of CA-M600's, one per speaker makes better sense.

Kept in mind that the most demanding and power hungry part of that speaker is the woofers. The midrange and tweeter use far less power compared to the woofers. In the bi-amp scenario, you still just have 200w available to the woofers, although the vertical configuration gives you a little advantage having a entire stereo amp's power supply on a single speaker. Using the CA-M600's, you now have 600w available to power and control those woofers.

As far as bi-wiring, I agree with Kr4, and will not disturb that hornet's nest.

I totally agree with Mattmiller. With my B&W 800d2,I tried with (1) MC275V, no big deal. Then added another "WOW..." what a different.
Because B&W demands higher power to be better, I added a pair of MC601 and never look back.
My experience with bi-amping was painful and bi-wiring was enjoyable with my B&W 800D2.

08-01-15: Zd542
If you could by a stereo amp that sounds better and has more power than 2
mono amps, why wouldn't that be the better choice?

I
agree with your view Zd. Carte blanche, I personally prefer the sound of the
Vitus SS-102 stereo amp which sounds a bit warmer and more organic
than the SM-102 mono's. That's in a perfect world, though as with most
audiophiles here I have some room and budget constraints which mean I
don't have the room to accommodate the big SS-102, nor the funds to also
buy the matching preamp (SL-102). I briefly considered the option of bi-
amping the new Vitus SS-025 stereo amp with my current SIA-025
integrated before I remembered the S5's are single wired, so I scrubbed
that option. I could have maybe gone for the SM-011 mono's, but don't
need that much power. Also in that case I would not have been able to
afford the SL-102. I still wanted more power and control & wanted to take
my system to the next level, so in my situation I decided the best solution
was to trade up my integrated amp for an SS-025 stereo amp which shares
the same chassis and price as my SIA-025, but has a LOT more power and
control & is designed in the same way as the SM-011 mono's. That move
leaves sufficient funds to add an SL-102 pre (incl: the requisite cables
and isolation). So it's a question of finding the best compromise within your
budget.

I don't have 802D, but 804S. I biwire. Does it make a difference? Probably not.

I drive the speakers with one MC275 and love the sound. I am finishing a couple of class D Hypex monoblocks to drive the woofers. I plan to get rid of the passive crossover between woofers and midrange and apply an active crossover there, keeping the tweeter-to-midrange passive crossover driven by the 275. My understanding is that active multi-amping (as in active crossovers) is the real deal. FWIW my subwoofers run below 80Hz while the MC275 takes it from there and up.

My experience across various B&W 800 series speakers is that both bi-amping and bi-wiring are worthwhile and discernable.
The improvements from bi-amping are obvious in improved both sound-staging precision and detail, while bi-wiring improvement in detail is only marginal.
Bi-amping is more hassle because need another pair of interconnects and pre-amp with dual outputs unless the amplifier has function to switch from stereo to bi-amp e.g. Cambridge Azur 851W.
One advantage of bi-amping class A or AB amplifiers over stereo/mono-blocks is the treble/mid-range remain longer in Class A.
I currently bi-amp my speakers (800D2 recently upgraded from 803D2) with 2 x CA2300 with no obvious power limitation.
I don't have comparison experience between 2xCA2300 to 2xCAM600 - ideally you need to demo.