There are speaker wires run down the passenger side. If you pull back the carpet just along the roll bar there, you'll find them. HOWEVER, they run back to where the stock amp is normally located, NOT to your radio. That means that you either need to 1) install a stock amp or 2) find and splice the correct wires under your dash or they won't work.
For my powered sub install, I initially spliced into the soundbar speakers but started getting random noise so I yanked it out. Now that I've installed an aftermarket stereo, I'm going to run RCA cables, which the factory system doesn't accommodate.