Does anyone here guide me on purchasing new O2 sensors for my '04 Forester XT? I'm going to be replacing them along with the catalytic converter, but looking at parts websites leaves me thoroughly confused. Does anyone have any suggestions regarding aftermarket vs OEM? I know the car needs a front and a back sensor, but I'm confused by my options, heated vs unheated, universal vs direct fit, etc. Can anyone here provide me with the parts I'm going to need?