What Amp? Yamaha V771 or A810, Pioneer VSX-2021, Onkyo 709 or 809...?

Hello everyone!
I’m in the process of acquiring an amp, I'm thinking of the Yamaha RX-V771 in Portugal I can buy it for 599 € (black) or the Pioneer VSX-2021 K (879 €) but for this budget difference I can think in the RX-A810 which I do not know the price yet but probably will not be very far of the VSX, and at this budget I can think as well on the Onkyo 709 or 809... The amp will feed my Monitor Audio B4 system an I will plug a LaCie lacinema HD.
I have an Ipad 32GB and Airplay would be welcome, But for 100 € I can buy YID W10 (for the Yamaha). This will be my center piece, I don’t have stereo amp and in the future I’m thinking in buying a pair of RX6 from MA... I’ve read the manuals of all amps and the racional choice apparently would be the V771, or not... I will replace a Yamaha RX-V 750 that never let me down in any way. I need some advice and some pro perspective.

Thanks!