The stock ones are actually very decent headers.. If repaired correctly they will provide years of life and they perform very well.. Aftermarket ones dont't give you much.. I'd put the money elsewhere
I agree with Ivan ^^^ The problem is finding someone who can weld them the right way.
TA performance headers are the best but a good alternative are the SE headers from tr customs. They are a good quality TA knock off for around 400 less.