From the image CC posted, the PCI-Express card's "components" (the stuff attached to it, the large fan cowling, and so forth) will be on the left side of the card. The Audio jack Block and the DRAM slots are both on the right side of the card. The only thing that will stick out on that side are a few savage metal pokers (the soldered on connection points of the components on the other side) which won't be low enough nor stick out far enough to interfere with the components.
Systems are typically designed in a way that puts the expansions slot in a "corner" of the motherboard. PCI-E andPCI cards have their components on them on the side that will face towards the side of the case that has that corner.
On another note, I've never seen a machine, (ever) that has the motherboard mounted on anything but the bottom (in the case of a desktop) or the right (in the case of towers) of the case. That isn't to say they don't exist, but that would usually mean the power supply is on the bottom of the case (or the case is gigantic) and the last time I've seen that was in a Mac II SE, and having the powersupply on the bottom isn't usually conducive to cooling.
