The PC is part of the whole package.
--The mechanical opening and closing of the engine valves.
--The electronically controlled triggering of the spark (your PC commander).
--The controlled metering of the fuel.
--Your exhaust system.
To be fair, you will only gain a marginal amount of HP from a PC and a exhaust system change. Many people think their bike is substantially more powerful after an exhaust swap...often this is because you lose your midrange and then get a "peaky" bike.
As pointed out before...if you're going to do this right, pay for a tuner and buy the whole package.
However, my philosophy is simply to buy a bigger bike because, basically, there is no amount of money you can spend that will make your R6 make the power of a 750. The amount of money you would have to spend in order to make a perceptible difference is better spent on better suspension, more comfortable leathers/helmets/boots/gloves, and at least two trackdays (those skills will stay with you for the rest of your life).
Bottom line: your bike is already pretty damned good completely stock. Here's a completely stock R6 hauling ass.
http://youtube.com/watch?v=DvSdwtlKc2I