you dont need any bottom end mods to see 185bhp out of a 1.7 zetec SE. Keep the rev limit south of 8k and youll be fine if you do head mods instead.
if you want over 200bhp and a higher rev limit then yes ARP's are wise for a start. Steel bottom ends are prohibitively expensive beyond that power level so youd be better off going to a engine swap if you want reliable 200bhp plus on a NA engine.