Do you biamp your B&Ws or other comparable brands?

I did passive biamp and realized that having powerful enough single amp works better.
Passive biamp in most cases stinks except using 2 identical amps. Even in this case one bigger amp wins with better tonal balance and better quiet sound precision.
Internal crossover may be of a high quality, but for biamp you need electronic crossover and built-in crossover removed or disconnected.

Absolutely agree with Czarivey. The best case scenario for passive bi-amping is 2 identical amps in a vertical configuration, however it is better to just have a single larger amp.

Center channel TBD

Isn't the obvious choice a B&W HTM2 Diamond?

Thanks guys.

I am using a 5 channel 250watt amplifier. I believe it is large enough to power the 803s, but I have been told that sending more power to the speaker with my current amp using biamping would improve the sound, especially at lower volumes. The matching is less of a concern here as i am using the same amp for everything.

Is bypassing the b&w crossover easy? Sounds complicated.

Regarding centers, I may get a different center as my cabinet isn't tall enough to house the tweeter for the matching center.

If I do not end up biamping, should I at least biwire?

I would like to biamp as I will be able to better utilize my amp. Otherwise, I'm wasting 3 channels of power in stereo mode, as opposed to just 1. But, I don't need to do biamp just for that reason alone. It must be simple enough to do and be worth the effort in sonic quality.

Adding a center speaker, you will then be using all 5 channels of the A51 for HT. Are you then going to disconnect everything and reconnect for bi-amp to do stereo only listening?

When you drive the 803D with a single channel, the majority of the power is being used by the LF input, with a small amount of the power being used by the HF input. So, to bi-amp, you are just adding more potential of power for the HF input that is just not necessary. I agree that more power can sound better at low volumes, however, that extra potential of power needs to be available for the LF input, not just extra power on the HF input.

Something that you may not be aware of is that the A51 will have more output capability when only using 2 channels as opposed to using all 5 channels. Check the measurements here for 2 channel vs 5 channel.

Is bypassing the b&w crossover easy?

No, as this will require serious disassembly of the speaker since the crossover of the 803D consists of 3 separate boards in different locations inside the speaker.

If I do not end up biamping, should I at least biwire?

This has been debated extensively on this forum with various opinions. IME, I prefer single wire with matching jumpers to replace the factory straps between the LF and HF connections, although I believe the 803D comes with a much better jumper than the typical gold plated brass factory strap. If you bi-wire, I believe most agree that it is best to use 2 separate runs of identical cable.

Regarding centers, I may get a different center as my cabinet isn't tall enough to house the tweeter for the matching center.

Understand, but it will definitely need to be a B&W.