B&W 804 diamond or previous 803D?

Could you please help me in choosing the better option? I can buy either of these two speakers but new 804 diamond cost by €1.150 more than second-hand 803D. What would be your advice?
I can't comment on the Euro speaker costs.
I will say that the Onkyo might actually have enough power to get the speakers playing, but is it the right kind of power?? There are so many options these days for power amps it is hard to recommend just one, from my perspective. All I can say is don't underpower them, you will be doing yourself a diservice.
What kind of sound do you like? I understand the B and W sound is precise and clean . You may want to balance that with a relatively warm power chain. A Cary tubed pre (I love 6SN7 tubes) into either a large and expensive tube power amp AtmaSphere?Manley?VTL etc.etc. or just a very powerful amp like the Sanders Sound amps which are made for Planar speakers but are applicable for other types as well. Good luck on your purchase I think you did fine.
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Hi Paul,

I appriciate your detailed answer. Today I bought 803D. This is upgrade for me so I am going to keep them for a long time. Very impressed with sound even with my current amplifier, so difficult to stop listening to them. But anyway I would like to upgrade my amplifier to use their whole potential. I am going to open a new topic for that. Hopefully see you and all others again there!
Dear All, based on all your responses, today I bought 803D. Thank you very much for making me this decision, since I really happy to get such divine sound improvement! Now I am going to ask you again about my next amplifier upgrade. I will do in another topic not to confuse you. Hope to see you all again there!