At what HP /rpm level are billet main caps and or stud girdle needed?

.....and if he is already starting with the best block available, it can be made significantly stronger for about a grand.
$6300 can buy some nice cylinder heads and camshaft.
I'm not arguing the point. That's why I didn't include an aftermarket block in my first response. He didn't ask for that. I simply made the later comment because they are out there.