ronemus

This could also be due to a bad water pump (had it happen to me); when the shaft bearing wears, it sucks air and blows the coolant out the overflow. The pump is easier and less expensive to change than head gaskets. You should do the timing belt at the same time, if you haven't already, since you'll have to remove it anyway.

Before replacing the bearins, check the runout on the rear disks - it can sometimes be confused with bad bearings.

The problem probably isn't warped rotors. Stock Subaru pads use an organic binder that cooks onto the rotors after a hard stop to a standstill. I went through several cycles of resurfacing rotors, only to have the pulsation return. The solution was aftermarket performance (not OEM replacement) pads - I used Hawk HPS. The cost is about what Subaru charges for OEM, but no pulsation and a firmer pedal to boot.