Dont get hung up on peak power. Its what the car does all the way through the rev range that counts.
For example my 172 was running only 182 bhp with roughly 165lb/ft (at the time) of basic mods (cams 182 mani etc) which sounds rubbish but with full interior, 25kg's of ICE, heavy Speedlines it was still able to beat my mates stock R32 on 3 back to back runs on a quarter mile plus some other 2ltr Turbo units it shouldnt have even got near really. Best time was 14.4
Its all in the set up and driveability not peak power.
The Supercharger conversion is insane in terms of out and out acceleration! If you had a go in one you'd change your views.
Insurance will go up but not by stupid amounts. Someone posted a quote up on a charger thread and it was in the mid 100's.
EVO's annual fuel and service bill alone would pay for a charger conversion