I think we may be in a similar boat. I am an extract/partial mash brewer also. I was fortunate enough to take first place in the Midwest Region for Nationals this year for my APA. It made me happy as pigs in $*%!. I didn't medal in final round- but I made min-BOS, so as far as I'm concerned I got 4th place!!
In my opinion it takes more than a bit of the luck of the draw to win contests. But it also takes brewing very good beer. By your scores you already do that. A lot of good advice in the replies I read above. My advice is this- review Mark Tanner's presentation from this year's AHA Conference. I am a committed extract brewer. I saw his presentation in person. I want to win contests and Mark has done so as an extract brewer for years. I assume by your question you want to do the same. By all means if you want to go all grain, make the jump. If you want to improve your current technique, check Mark's advice and feel free to contact me.