Assuming good tuning:

~444hp equals about 290.8psi BMEP
~491hp equals about 321.5psi BMEP
~571hp equals about 374.2psi BMEP

An estimated 350psi BMEP is about the "safe" limit for engines sleeved the way ours are. If you're looking for a "glory run" car then you could probably hit 400psi BMEP and around 600hp, but then you would eventually experience failure modes which would be associated with cylinder wall stretching/walking.

Also, aluminum's lack of fatigue limit would mean that failure would be an inevitability - the question would be "when" and this would be associated almost directly with ignition timing so that peak cylinder pressure is minimized.

BMEP being one power-related metric. The other is RPM. If the redline is raised 1000 rpm, and the head is modified to support the additional flow required, then 16% more power is available without additional strain on the cylinder walls. Might as well use those fancy high-strength pistons and rods for something...the question is whether the balance shafts can take the additional speed without spinning bearings.

Keep in mind that a Porsche 911 GT2 makes 520hp, and that's not necessarily at the wheel, and it has a closed deck, AND it has 0.4L more displacement.