The sway bar upgrade will not (actually cannot) make your ride stiffer. The sway bar simply provides much more control, adds stability of the machine as well as steering accuracy. And does so without adding any stiffness or harshness of ride.
However, you certainly can get a much stiffer ride with an aftermarket shock/spring combination. Thought this is not necessarily so. The wrong shock setup can really make for a stiff, harsh, uncomfortable ride. Don't get me wrong. Going with a better shock can really give you a great deal of improvement without any significant change in ride comfort. But just because they are new and even expensive, does not guarantee a comfortable ride.
Though the shocks and sway bar work together to (Ideally) provide the best possible ride and handling. And though the purposes of the sway bar and shocks do overlap somewhat. Both have a specific, important and separate function.
Some have ended up with a stiff or harsh ride when they attempted to compensate for the weak sway bar with too stiff (either hydraulically, spring rate, or both) shocks.
It really isn't that difficult to get it right. I'm not trying to discourage anyone from improving their ride. And you don't have to ride like a racer to enjoy the benefits of these upgrades. But it pays to do a bit of homework before you spend your money.