I've struggled with the problem of airflow in my PC at home for over a year now. My situation is a little atypical; I have the second-best desktop processor money can buy in my rig at home, and unlike all the other tech-spec "My PC is better than yours!" geeks wandering around out there, I'm actually using 100% of that CPU's power. (video encoding completely dimes my overclocked i7-5930k out)
I've gone through the xClio A380 and the Rosewill Blackhawk cases in the last year, and neither one of them could really get my CPU idle temps below 38 degrees Celsius, with full load temps around 55 degrees Celsius. If you look up those cases, you'll also notice that one of their major selling points is fans and air movement. Both cases have at least one 250mm fan and at least one 140mm fan, and claim to have incredibly good airflow. In light of that, I figured the problem must be my HSF. I bought one of the largest pre-built liquid coolers money could buy (Thermaltake Water3.0), and still struggled considerably with CPU temps.
After failing miserably in this endeavor in the last year, I sat down to actually look at this from a physics standpoint. "Why is my pre-built chassis that's loaded with fans simply not moving air?"
I realized that the terms "negative airflow" and "positive airflow" are actually major players in how well your chassis will keep itself cool. I also found that, unsurprisingly, most PC chassis aren't really designed around the idea of positive or negative airflow, and are built more with cosmetics in mind for the end user. Geeks do like their flashy toys, after all. The last thing I noted was that "dust filters" SIGNIFICANTLY slow down airflow.
For positive/negative airflow, what this means is that you have to be putting the same amount of air into your PC as you're pushing out in order to make air actually flow. You also have to seal up "breathing holes" in the chassis to basically force the air to move along the drafting pathway in your computer the way that you want it to. In relation to "dust filters" and airflow in this manner, dust filters effectively stop 50% of the airflow coming into the fan on the front of a chassis. So, you'd need a fan that was pushing twice as much air on the front end as the one on the back end of your PC to compensate, at least in theory. Not to mention you have to clean the dust filters once a month, which any tech will attest to as being a freaking nightmare in many chassis.
Have I bored you yet with tech details? I bored myself out pretty bad. For me, time is money and I have very little free time. I don't have the time to dig through NewEgg or TigerDirect to try and analyze all the chassis they have and find the one that has the airflow that I'm looking for, then take a gamble on if it will actually work once it gets shipped to my apartment.
Enter the concept of the "open chassis".
Several vendors have done an open-style computer case, and as long as they're built right, they have a lot of advantages in this area. For starters, they basically eliminate the airflow problems your computer has because they're directly vented out into the room. There's no place for hot air to stagnate in them! They also look really nice. As a respectable gentlemen, I'll be the first to firmly say that "looks don't matter", but having them to back up an otherwise admirable "core framework" is a nice plus.
I ended up going with the Thermaltake P3 open case, and was amazed that it completely solved my airflow and heating issues from Day 1. My computer idles at 31 degrees Celsius. It hits 43 degrees under full load. Because of this, it's offered me that much more room for overclocking potential in my CPU if I choose to go down that road. It's actually so cool, that after I re-greased the heatsink on my Radeon R9 Fury graphics card, the card no longer even turns it's fans on to stay cool unless I'm in a game and am pushing it hard. I've never even seen that be the case before.
In summary, the Thermaltake P3 is the best $119 chassis I've ever bought. It beats out the chassis that I spent over twice that dollar amount on. I'd highly recommend it even if you aren't directly struggling with heating problems purely for the looks aspect, and that it does it's job well and for a great price point.