Usually there's no need to wait until you have your graphics card. The only exception to this is if you have a huge graphics card and you're not sure if it would fit into your case. But even then, you don't really have many options. Either remove the shroud (voiding your warranty in the process) or exchange the card for a smaller one. And there's a third, forth and fifth option of course--change your motherboard, CPU cooler or case. But I don't think you'll want to do that.