I found that your case can make a bigger difference in your overall temps if you're using air cooling regardless of the number of fans you have installed.
I had a CoolerMaster Cosmos 1000 - loved the look of the case, but the case had piss poor cooling with air even though it was a full tower. I tried multiple air coolers for the CPU and none of them really made any difference. I eventually went with a Corsair H50 AIO and it dropped the CPU temps by a good 4-5C. Air cooling sucked in this tower.
I moved to a Fractal Design Arc XL - much more open and I even went the route of mounting the HDDs in the spare 5.25" bays and completely removing the HDD cages to improve air flow. Having multiple front and bottom intake fans with multiple top and rear exhaust fans, temps were a bit lower than the Cosmos 1000 case, but still higher than the case I'm using now.
I moved to the CM HAF XB Evo for two reasons. 1 - the MB mounts parallel to the ground so the GPU isn't hanging (had horrible GPU sag in my last case) and 2 - with how the MB sits, everything is just exhausting hot air up and not into other components. GPU temps went down by 4-5 degrees overall and all I was using was a total of 4 fans on the case. 2 exhaust fans (1 - 120mm on the rear and 1 - 200mm on top) and 2 fans for intake (was for the AIO radiator mounted on the front and they were pushing cool air into the radiator).
The HAF XB Evo isn't the prettiest case to look at, but then again, I'm not looking at it. The case, however, has better cooling over the other couple of full towers I used to use.