Looking to upgrade most of my system. HELP!

gnarlycore

Hi there I'm kind of a newb when it comes to HT but I've been looking to upgrade my setup and was maybe looking for some pointers from you pros. I'm currently using an old Yamaha 5.1 receiver and the polk 6500 set I believe, the all in one box deal I'm sure you guys are familiar with it. So saying I have maybe $800-$1000 to spend on upgrading, what would you guys suggest? Would like to upgrade the Receiver, then center channel (which I found very weak) then the others. thanks!