For SLI information, google is your friend:
http://www.pcmech.com/article/sli-technology/
Cases, cases!
Write down your requirements, particularly around quiet operation, cooling fan requirements, number of internal / external drive bays, toolfree operation and appearance / lighting (this latter leaves me totally cold). Probably more, but that's a start.
Select case, based on the above, assuming that EMR shielding is equal for all (it isn't, but how are you going to tell).
If buying from a website, there are often reader reviews that give clues.
Don't expect the cheapest case to be well finished (but then many expensive ones aren't either).
Read the small print - some cases come with a lot more screws, cables, adaptors than others.
SD