If this is your “last system I will ever need to buy”, you should focus on brands that you can be proud of owning. If you’re not sure, then it’s not time to buy yet.
It’s a good start coming here for discussion.
Every single component is important - Speakers/subs, AVR, Projector.
The Epson LS12000 is an excellent choice, so you got my vote here.
Onkyo? Would never buy one for myself.
B&W 800D, 801D, 802D? If they are in excellent condition and the price is awesome, I say yes. Other B&W speakers? Hells no!