The 680i is going to be more expensive but it offers more features all around it just depends on how much you want to spend. As for the case I love mine (see sig) but it's very expensive, the Antec P180 and Antec Nine Hundred seem to be fairly popular and the Antec Sonata is a nice looking mid-tower. Cases are all about personal preferance, go on Newegg and look around to find something you like then come back and ask if it's any good.
If your wondering why all three suggestions were Antec it's because I've owned them before and Antec makes solid quiet and reletively inexpensive cases. Here is a great deal on the Sonata $103
I'm not doing this to make you doubt your decision. I am sending a cautionary note to you. I have the nine hundy and a dremel, together you can create cable management the p182 gives you. Buy a dremel for 60 bucks, create some cable routing holes and you'll be set. However, if you decide to not get a dremel, you will have a hard time routing cables, however it is possible to get a decent routing job. I just helped a friend build a his rig in a p182 and I cant even imagine not having holes to route cables behind the mobo. Anyway, this isnt a cable routing thread, just letting you know what you'll be getting into with that 900. Its an awesome case, but it makes you earn the performance it offers.
Edit: If price is a consideration for you, you can purchase a 680i LT which functions identical to the full 680i but with some minor differences. You can save 50.00-60.00 going that route. Good choices and good luck!