The Demand series are very nice speakers by all accounts, and I think worthy of upgrading to. The BPs, not so much.
At that price point there are some other speakers I’d consider too. Some will recommend the new Polks, I like the JBL HDIs. Revel and Monitor Audio, too.
Anyway... if your heart is set on the D17, I’d say go for it. The Marantz (either one mentioned above) should work well. I think I would look at adding an amp for the front three just to make certain I have the headroom for dynamic peaks... but if you aren’t the kind that is hoping to hear Godzilla eating the world right next to you, then you may just be fine.