600W is the absolute limit the design will take with the highpass from post #336
in place... I wouldn't do a watt more than that. And you will absolutely need that highpass... it's what'll keep the drivers from clanking below the corner. My 360W suggestion was before Hornresp added that awesome simulation feature, and had to more or less guess based on the Reckhorn and diaphragm displacement graph.
As is, they will be very close to clanking above the corner as well if you give them that much power. Xmech is 28mm IIRC, and you will be close if you run them full out on 600W. You still need to stay around 360W if you want the drivers to stay within Xmax. That said, at 600W in quarter space at one meter, you're talking over 120dB each.
Your house might give up before those drivers do
In other words, I would run the Crowns and add a MiniDSP balanced. You've got the amps, they're not crazy overpowered for the design, might as well use them
FWIW, the difference between 360W and 600W in SPL on this design is minimal. You gain perhaps 3dB... that's it.