With PCI-Express you don't need to worry about the bit width. Instead all you really need to know is how many lanes it has (ie x1, x2, x4, x8, x16). A card with fewer lanes will always fit in any lot that has more - in other words, you can fit a x1 sound card into a x16 extra graphics card slot. You cannot fit a card with more lanes into a slot with fewer (it won't physically fit).