Yes especially if you're using high end gpus. Those kinds of gpus are long and wont fit in some standard cases. Also, if you're going to crossfire, you're going to want a sturdy case to house 2 gpus and a an atx board. Some cheap cases are definetly sturdy but the work quality sucks (sharp edges on the cut out parts). A fractal core 1000 is a good sturdy micro atx case that can house that build (i think) although i dont think you can sli/crossfire with that thing unless its compatible with an atx mobo.
Long story, short, google is your best friend. Its always nice to research the parts you want just to be on the safe side of things. Always check the compatibility of your mobo , cpu, and case and you'll be fine.
- Renzo