In my personal opinion:
Some canned air and cable straps would be at the top of my list.
If the radiator already has a fan on it why add another one. If it doesn't pull enough air through it then a higher volume fan is in order. As for the PCI cover plates and the grid to the left of them running down the side, the best thing is to get some black duct tape and mask them up. That's the last thing I did to mine after putting it all together. They're air leaks and they do affect the air flow. It's a short circuit to the exhaust fans.
As for the fan behind the power supply that's a subjective call. Me? I'd mask it off.
And that fan in the front is just in the way. Take it out.
Now as for the fans you have in it and considering your post is basically wanting to add fans to cover what you interpret as a heat problem could be resolved by replacing the fans in the roof with higher performance models. I gave these Cougar Vortex babies a go in my recent built and couldn't be happier with them. Quiet while moving large volumes of air. COUGAR CF-V12HPB Vortex Hydro-Dynamic-Bearing (Fluid) 300,000 Hours 12CM Silent Cooling Fan with Pulse Width Modulation (Black) - Newegg.com
You don't always have to add extra fans to over come a heat problem. Some times cleaning the inside will take care of a lot of it. Canned air and a 1" horsehair brush work wonders. And sometimes it's as simple as swapping the current fans out for better performing ones. But please, try cleaning the inside of that case and tidy up the wiring. It does make a difference.
---------- Post added at 10:31 PM ---------- Previous post was at 10:29 PM ----------
Need to read reviews on those types of products. I did. The DOA and high failure rate made me think twice about getting one.