I noticed on the H500 that the included 200mm fans on front are significantly blocked by the chassis, due the chassis being designed main for 3 smaller fans. I was bored so decided to see if removing this excess material would help any. 
 
I removed the rivets holding the front on and removed the front. Scribed around the fans (not the ears) then removed the fans. I completed the circle by connecting / continuing the circle where the ears had prevented me from doing while the fan was mounted. I used a Dremel with a cutting wheel and cut out all the material using the scribe mark as my guide. Cleaned it all up nicely making sure there were no sharp edges. I put the front part of the case back in place and riveted in the same locations as stock. I was not expecting much but actually got what I consider a significant improvement. I had already gotten a max temp average of 72C by running a level of Ready or Not multiple times. I did this again after the mod and surprisingly (I guess), my average was 67.5. My CPU, which is also air cooled, dropped about 4 degrees. Worth it? I don't know but it cost me nothing and my system is running cooler. I should also note that the 72C temp was obtained at a cooler ambient temperature so the improvement may actually be in even slightly better.