Ya that would be a bit small wouldn't it. Nah keep the board you have just wanted to warn you about the audio. The common complaint with that board is getting the audio to work that's all. That was from the newegg comments.
As for case just pick out something you like. That's more of a aesthetic thing then performance. Just make sure it supports standard ATX motherboards. I guess the name brands people like are Antec, coolermaster, thermaltake to name some. I'm sure others here have/can mention additional ideas for you. My favorite case is the ANtec performance series. I would so get the Antec p193 if I had money to burn.
Ya know have fun picking out a case. that has nothing to do with how fast or stable your system is. Although there is the power supply but *shrug.