Thats the thing exactly, say no more.
As far as the capacity of the S30 rear end itself to handle power goes, using available aftermarket parts including rod ended wishbones and beefing up the diff mounting arrangement, what, 4-500WHP??? Basically whatever a R200LSD will handle???
EDIT: But with 4/500WHP no problem using a S13/14 rear end, should work OK with an upgraded S30 front.