Man I have a 08, and had that same damn leak. Go to Subaru and get the MLS gaskets. They are the new multilayer steal gaskets with lips on them. Now I always get different answers from people about getting the head machined. I was going to but that wanted me to take the head apart and take the cams out and so on. I told my buddy and we have worked on my 04 STi and many other cars. I cleaned the heads by hand, and since my motor never over heated while I drove it with that leak for a year, we put the heads and new gaskets on.
You do not need new head studs unless they have stretched badly. Now you miles are about the same mine were when I pulled my motor, so you should be fine. You do not have to pull the motor to change the head gaskets FYI. I did it because we were bored and had a month to do it. I also changed the water pump, thermostat and many other things all with OEM Subaru parts.
If you have the time and money, go all Subaru OEM and replace the gaskets. If not drive it like I did for a year or more. Just make sure you check the oil and coolant every week. I was burning coolant but it was never mixed with oil.