Bell Canto C5i Integrated Amp with B&W Nautilus 803 Speakers. A Question

Besides room size, treatment and placement, how loud do you listen? I used to have a BC C5i that I used with ~88 dB efficient speakers (first Spendor SP 1/2E and the Golden Ear Triton 7s) in a medium size room and had no problem listening at average levels of 85 dB or so.  It is when you really want to crank things up (mid-90 dB or higher) that you really need the higher power amps. Remember that watts / sound level is a logarithmic relationship, not a linear one. For example, if it takes you 1watt to hit 75 dB, it'll take 10 watts to hit 85 dB, or 100 watts to hit 95 dB -- in other words, power requirement goes up 10 times for each 10 dB increase in listening volume.

Final suggestion -- invest a few dollars in a sound level meter or sound level app for your phone.  That is the best way to get a good idea of just how loud YOU listen.  Remember that one's person's "moderate" volume may be "extremely loud" or "soft" for others.

Yes make sure it can go loud enough otherwise c5i is a very good sounding and versatile choice.

Thanks alot for your input.

Your amp will be seriously underpowered for the intended application.  Nothing wrong with class D amplification, in fact I prefer it with my B&W along with a tube preamp.  IME 200 watts would be a minimum figure.  
A loud listening level for me is in the lower 80db range with peaks in the lower 90 db range.  Normal listening levels are 5-10 db less than that.  So, the power required is not for head banging sound levels.  The power is necessary for a balanced sound output.  Not enough power results in thinness and over- emphasis of the top end.  I currently have N802 and Concept 90 in two of my systems so I’m not talking theoretically or repeating ridiculous crap like you need Classe or McIntosh amps to match B&W.

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Interesting -- I listen at the 80 to 85 dB level and like the sound of my relatively low-powered Schiit Aegir much better than the VTV class D amp that had 150 watts/ch.  No issues with thinness or an overemphasized top end in my system. Just goes to show that everyone needs to figure out what works best for them, not someone else.