Custom Computer Build?

Im building myself a computer right now and its going to be mostly for gaming. i want it to be powerful enough to run games in the future i dont want it to be "obsolete" in a couple of months.i know how to put everything together. And im interested in running a second graphics card in SLI but i dont know too much about that. Someone suggested getting two hard drives and putting them in RAID 0 configuration but i dont know what that is. so if you guys could suggest hard drives for me and links possibly. i am interested in overclocking both video cards if i get them. will i be able to do that with this motherboard and could you guys tell me a little bit more about it? And as for the heat. i am going to need something to get rid of the heat for all of it but i dont know where to start to solve that problem. so suggestions for that would be nice. and last i dont know where to buy a case for it all. thanks for all the help. i chose the audio card because it was cheap lol :)