Opinions: Martin Logan Renaissance 15a vs. Bowers & Wilkins 800D3

One advantage (a big one IMO) with going to separates instead of an integrated amp/preamp is the flexibility of being able to change one or the other out in the future. Also separates will likely give you better SQ with the B&W's as they are very revealing.  

Not sure about a tuner recommendation... I stream through Roon for radio stations so don't use one.

I would recommend a separate transport & DAC instead of a CD player. In regard to transports, a lot of people are using "Projects" TOTL or "Jays". As far as DAC's, I like the Musetec DA005 (great player / especially for the money), but there are a ton of other good ones out there as well.    

+1 audphile1 

Another good amp choice would be one of the larger Magnus Audio (out of California) amps. The MA400 makes my 802D's sing nicely.