Get the right size computer case

Most people building a computer will get a "ATX Full Tower" case that honestly is just too big for their real needs.  The ATX case is the Hummer of the computer builders world.  It will have 6 DVD drive slots and they will use one of those slots.  It will have 6 hard drive slots and they will tape their tiny SSD drive to the side of one of them.  They pay extra for the extra size, the extra shipping, it takes up tons more space, it is much heavier to carry around, etc.  

The real case size you want is just big enough to contain all of your needs.  For most people, this will be what is called the micro-ATX form factor.  This is a smaller size case for a smaller motherboard that still has everything you need.
- designed for good airflow
- silent fans
- dust filter
- designed for long cards
- fits normal power supply size
- has built in sound supression 

This case is the best one I am aware of at the moment for price and functionality.  Do yourself a favor and start with a the right size case!

(... and if you really insist on full ATX case, consider this one which I think is currently the best one around.)