Up to how much power would you guys recommend a aftermarket seal and springs (Apex/Springs, side, corner, and related) on a boosted application?

My goals are in the 450hp range street car build with (occasional) circuit style weekend racing in mind. Although I'm a big fan of using quality OEM parts, I also wouldn't want to stress parts past it's original engineered tolerance.

Irons and housings are stock port for now.
(Open to port ideas to achieve maximum mid & top range power up to 8k rpm)
The parts I currently have are:

9.4 rotors
FD irons
FD housings
New RX8 E-shaft
New OEM rotor bearings
New OEM stationary gear bearings (FD)

Experienced input is greatly appreciated. thanks!