I had the same issue. I got the Mishimoto radiator and it has been good to me. I use Subaru green coolant and their additive. Now is a good time to buy new radiator hoses as well. Might as well get a new t-stat. If you have an OEM radiator with no cap then you will have to add a tube to the overflow reservoir. Not hard to do this all yourself. If you get new hoses the upper one will need to be trimmed to clear the fans. On the Mishimoto I just filled the petcock with sealant to ensure it never leaks. Good luck.
You did good making it to 198k miles. Might as well just get that timing belt done as well.
Later I will write a thread concerning burping the radiator. This gets asked so much and I haven't seen a good write up yet. It sounds like you are doing it right though.