As unfortunate as it is, most cars don't come stock with a stance that is good enough to satisfy a great majority of car enthusiasts. Automotive companies have a tendency to give you good options for wheel diameter but not the actual width of the wheel and tire. To give your car a good stance, it helps if your wheels are flush with the fender openings instead of inset by a couple of inches. That means you have to upgrade from the usual factory tire width of 225-275mm to something more like 315mm in the rear. Sure, it's expensive but it looks fantastic. You typically need at least a 10" wheel to fit a tire that size and factory wheels seem to be more like 7.5" to 9" most of the time. On the bright side, that gives you an excuse to go get some new, sporty, five spoke wheels! Please do yourself a favor and avoid chrome wheels, though. My favorite wheels are matte black, brushed aluminium, or gunmetal with a simple five spoke (or split five spoke) setup. It's clean, sporty, and intimidating.
With a good combination of some clean and sporty wheels, thick performance tires, lowering springs and shocks as well as a little negative camber, you can make even a V6 Challenger look like the heavily modified R/T I've posted above. For JDM cars like the S2000, 350Z, and 240SX, I am all about the Volk wheels. They are very expensive but you will turn more than a few heads with an aggressive stance. That seems to be something people overlook quite a bit when trying to trick out their new car; the stance. Forget the forced induction and massive body kit for a while and just focus on your suspension, wheels, and tires. If you can fill out those wheel wells with a good looking wheel/tire combination and drop your vehicle an inch or two, you'd be surprised how far that will take you.