HOnestly there's a fine "blance". Bolt ons are a must to support the power adders. The car must breath better; CAI, headers, true dual exhaust system.
The car must handle; swaybars, shocks/struts
The car must handle the extra power; clutch, transmission, rear end and coolant system. Not to mention 4 or 6 pistion break system.
These are a few things and it doesn't ahve to be in that order. The problem comes in when you try to go really crazy, like triple the stock HP. There's more to making the engine "right" before you can slam those gears.
But in the long run... if you are not going to a race track... just driving on the street, etc. You are ok just buying the systems that are meant for a stock car. yeah,it may only yeld 80-100HP extra, but at least its safe.