Calculate the power drain for the components you have selected. Make sure you've included all of them. Then decide on any future expansion you would like to do and purchase a PSU based on that.
The case you would have to purchase depends on a number of factors. The ammount of drives you want inside, the form factor of the peripherals you have selected, the PSU you will be purchasing, the cooling system you wish to have (maybe a bit extravegant that one) etc, the size of your motherboard, whether you want card readers, front USB ports etc.
Once you have all this information you can pick which kind you need and the one you like the most out of them.
To calculate PSU Size have a look at This or This page
Cases are too subjective for someone to choose one for you. You could buy anything from This to This Perhaps have a look at http://www.xcase.co.uk/ for some ideas. IMHO you will only need a Mini Tower case.
Hope this helps.
