Replacing two blown pistons and trying to decide what to do.

Cylinder sleeves and conrods are perfect and completely undamaged. Miraculously, only damage was to the pistons and few valves. See pics.

Trying to decide how to proceed, and whether there is any value to replacing all 8 pistons while I'm in there. And, if so, what should they be replaced with.

I do plan to add some performance mods, hopefully getting bhp into low 600s and torque into the high 700s.

My questions are,

What sort of power is required for forged pistons to become necessary?

Whether and what extent they will improve the life of the motor?

Are they worth it ($2k for a set of Mahle forged vs. $500 for a set of German Klobenshmidts)?