I think 550whp is like the minimum most supercharged cars put out. Theres N/A cam cars out there that are over 500whp. Not sure where you have seen 450whp supercharged cars, unless they're pushing 5psi or something. 600whp is easily obtainable on a stock engine with S/C.
2010 Camaro SS LS3 - Night Fury Cam, PAC1208 Double Springs, SP Long Tube Headers, Cold Air Inductions CAI, SLP 25% UDP, Fuel/Coolant Hose Relo Kit, Magnaflow Axleback, AAM 3.91, Eaton TruTrac, JRE Billet End Caps, GFORCE1320 1000hp Axles, DynaTech 1-pc Driveshaft, Pfadt Trailing/Toe Rods/Diff Bushings