@murphyb
With your B&W 805 D3 speakers, I wouldn't use that Marantz SR6009 receiver if you want to get the best sound quality of your system. It isn't about power output or ratings but it's all about audio performance or sound quality.
That Marantz SR6009 or any Japanese mass produced AV receivers will not sound good especially for stereo music playbacks or performances.
Your B&W 805 D3 are great sounding speakers and they deserve much better quality electronics than what you currently have.
Let me ask you first, are you doing only stereo or surrounds for HT?
If you are only doing stereo, then you should get either good quality stereo integrated amp or separates (stereo preamp + power amp).
There are good quality stereo integrated amps or stereo separates out there.
For your B&W 805 D3 speakers I would highly recommend the following stereo integrated amps :
* Rotel RA-1592 stereo integrated $2500.
* Parasound Halo Integrated ($2500 to $3k).
* Classe Sigma 2200i stereo integrated amp ($5500). This is a direct digital integrated amp.
* Naim Uniti Nova ($7500). The Naim Uniti Nova is basically a digital streamer/DAC/integrated amp all in a single chassis. Highly recommended!!
* Rega Elicit-R stereo integrated amp $3k.
* NAD M32 direct digital stereo integrated amp.
The above stereo integrated amps will way outperform and will sound way better than your Marantz SR6009 av receiver or any AV receivers.
It would be such a waste to have these wonderful B&W 805 D3 speakers paired with the Marantz SR6009 av receiver.
Again, it isn't about power ratings or power outputs but all about the quality of currents in the signal paths that reproduces beautiful music and sound. The parts quality, circuit design topologies, power supplies, etc, etc.
Besides, those Japanese mass produced AV receivers manufacturers such as Denon, Marantz, Onkyo/Integra, Yamaha, Pioneer, Sony always tend to boost up their power ratings only with one or two channels driven and measured at high distortion levels. The power outputs will drop significantly with more than two channels driven measured at low distortion levels. And these AV receivers will not be able to handle low impedance loads.
You should definitely upgrade from your Marantz SR6009 receiver and get good quality electronics that will be able to drive these speakers at their full potential thus optimize the performance of your speakers. The Marantz SR6009 is more suitable for budget speakers such as lower end series B&W 600 series and the likes.
If you're doing surrounds, I would suggest that you get high end AV receivers eg Arcam AVR 850/550, Rotel RAP-1580, NAD T787/T777 v3, Cambridge Audio CXR200 or get good quality AV separates such as the Classe Sigma SSP + Classe Sigma Amp5 power amp combo or the Classe Sigma SSP + Rotel RMB-1585 power amp combo, or the NAD M17 + NAD M27 combo, or the new Marantz AV8805 or AV8802 + Rotel RMB-1585 power amp combo, or the Anthem AVM60 + Rotel RMB-1585 / Classe Sigma Amp5 power amp combo.