this forum highlights the fact that people can talk out of their anuses and get away with it.
the best way to find out what's very important and whether a PhD holds weight is to call/talk to a program director. straight from the horse's mouth.
a good board score is necessary - it's like a benchmark. its like needing a vagina and 2X chromasomes to get into an all-women's college. scoring poorly doesn't mean it won't matter, it means there's a good chance you've lost before you started.
PhD isn't necessary, but it DOES tell the program that you have the capability of bringing with you lots of research to their program, which they like. so yes, it means something.
look at the match statistics and see how many PhD's got in vs. those applied, etc, and analyze the stats. OP, you say it confers an advantage. so ask around, perhaps at your school's program's director, and see what he/she says.
chances are, you'll get a similar answer from most other programs. Honestly, if you have questions about match, the best place to go to is the program director at your program, not the people around here; its the best info source you can possibly tap. but do be sure to share your info with everyone, even tho ppl like me may end up questioning it anyway.