Well, if I had to pick among those listed, at those prices, I would probably go with the Project One, because it is about half as expensive. If they were all the same price, I would want the Pioneer SX-1250 (I have one and really like it). But, like several other people have already said, I would go with separates at the prices you are looking at. The Pioneer SX-1250 is a great receiver, but we are talking about a piece of gear that is over 40 years old, and also one should consider what else one could buy for that price.
Honestly, I am somewhat tempted to sell my SX-1250, given the crazy prices they are going for these days. But I am very used to it (I have owned it since the early 1980's; I paid $325 for mine in near mint condition with box and manual, which I still have and the receiver is still in near mint condition). Also, it is a bother to sell things, so that also makes me disinclined to sell it. But there is no way I would pay $2900 for one.
It is a very attractive unit, it performs well in all its parts (tuner, preamp, power amp), and the controls are logically arranged. I can see why people want one. But, again, what else could one buy for the same amount or less? You could easily get more power (though most people don't need more power), or a better tuner, or....
