I really wish people would stop blindly suggesting top fans as exhaust. Heat does rise, but not when you've got a fan moving it. I changed my top two fans to intake and it dropped CPU temps by 5C.
I really like what you've done with your setup and would probably be what I would do as well. Some things I would tinker with just for fun is removing the back exhaust and seeing if temps change. It works best the more open the back of your case is (removing expansion slot grills and fan grills), but the positive pressure from intake should push everything out better than a single fan. If temps are same or better you just got less noise for solid performance. Same thing with the top back intake, try getting rid of it and taping over it. If you have room, but it looks like you don't, you might also try moving one of those other fans into the 5.25" drive bay for intake.
Changing fans is easy, just try it see if you like it and stick with which ever worked better. In all honesty, all case fan setups are a YMMV issue dependent on too many variables to keep track of. What works for some might not work for others, so test it out for yourself and see.