amp wiring 2007 yaris sedan

[patm]

I was told by one installer that to hook up the amp (in trunk) to front speakers of my 2007 yaris sedan the door panels did not have to be removed. I assume he would run wire from the amp to the front of the car (radio) and splice into the factory wiring that were already hooked up to the font speakers. Am I correct and if yes is this the proper way to do it or is it best to wire directly from amp to speakers. It seems the first way is easier and cheaper.