This all started with a low jump number guy asking for help and turned into a pissing match. This is a big problem all round at many Dz's. What canopy is right for the new guy? Get back on topic.
You've already been jumping a 9-cell so stick with that. I'm not saying there arnt some great 7-cells, I had a triathlon for years and loved it. Just watch how fast you downsize, it can kill you trying to keep up with your friends or trying to be cool.
I find it odd that wing loading hasn't become a a big part of this. You should talk to your rigger and fellow skydivers and figure out what a proper wing loading is for your experience level. Then start looking for a canopy, 7-cell or 9-cell.