Hi Katelynn, congratulations on that nice little Springfield XD9SC 9mm! Decent pistol you have there even though this type of handgun or the 9x19mm cartridge is far from my first choice in a handgun or cartridge - my reasons in the proceeding paragraphs. But we all have our preferences and to each is own with whatever they choose. I am a from the old-school guy; with my preference in handguns being the revolver, as I simply love the versatility, reliability, and simple operation of a good old wheelgun.
It doesn't get much more versatile than a nice double action .357 Magnum revolver as one can shoot anything from mild .38 Specials for target shooting or practice, .38 Special +P hollowpoint loads that have a good balance between effective performance and mild recoil and blast, all the way up to full bore .357 Magnum loads for serious protection against both two and four-legged predators up to small to mid-size black bear when loaded with 158-grain or heavier flat nosed hard cast bullets. Still for bears, I recommend a .41 Magnum and up, but the .357 Mag on bears with heavy 180 to 200 grain hard cast, flat nosed bullets with full powder charges behind them sure beats anything less such as the 9x19mm, .38 Special, .40 S&W, or even the .45 ACP by a hefty margin, and is also useful for hunting medium sized game such as deer. A good double-action .357 Magnum revolver is a handgun that can serve many purposes really well whereas the 9mm pistol you have is more or less a single purpose handgun. Again not knocking that 9mm you have, as it's not a bad combination, but for me I swear by the versatile, proven, reliable, and hard hitting .357 Magnum cartridge and revolver combination - and should you get yourself another handgun, I think you'll love a nice .357 Mag wheelgun and it is by far my top favorite! :)
For auto pistols intended for serious personal or home defense against two-legged predators, the .45 ACP pretty much rules them all and is my first choice, with the .40 S&W coming in second place. If you really like your Springfield XD9SC lots, maybe consider moving up to a .40 or .45 cal version next. I know a fellow who serves in the US Army and while he was living in Alabama, he carried a Springfield XD in .45 ACP and really liked it. As your intended role for your pistol is more than likely for protection, I would use the most powerful 9x19mm +P loads with 115 to 127-grain jacketed hollow-point bullets that your pistol can safely handle (and that you can shoot comfortably) for maximum effectiveness should you ever have to use your pistol for protection. Keep the lighter 9mm loads for target practice and fun shooting at the range as the hotter ammo accelerates wear and tear on guns. Shot placement is most important, but the stopping power from both physical and terminal ballistics is also key to effectiveness. The time proven .357 Magnum is still the measuring stick for handgun cartridge stopping power as to which other handgun cartridges are judged as we have a very powerful round that fires a mid-bore, medium weight bullet at very high velocities that creates lots of impact energy and hydrostatic shock. It is the very high hydrostatic shock effect combined with effective bullet performance that makes the .357 Magnum so effective against two-legged predators, and also four-legged varieties up to black bear. As for the .45 ACP cartridge, it's principles are more or less the opposite to the .357 Magnum as we have a large caliber, heavy bullet moving at a much slower velocity. But like the .357 Magnum, the .45 ACP is a very effective and time proven self-defense and service round, especially with 200-grain and up jacketed hollow-point loads at +P power levels or even just standard pressure loads. The .40 S&W provides the best of both worlds for the most part and this is why so many law-enforcement agencies in North America and in many countries abroad have replaced their 9x19mm pistols with .40 S&W caliber models as the 9x19mm has mediocre stopping power. When the chips are down, I'll take the .357 Magnum as my first, with the .45 in second when using a handgun to deal with hostile threats. As for lesser cartridges like the 9x19mm and under such as .380 ACP, I despise these with passion and they are a non-starter as far as I'm concerned. In my eyes, I view handgun calibers like the .380, 9x19mm, and many .38 Special loads as ideal choices for a secondary handgun that serves as backup in case the main sidearm (and heavier artillery) such as the .357 Magnum, .45, or even .40 should fail or run out of ammo.
For more information on terminal ballistics, this article is a very good read: http://www.gunthorp.com/Terminal%20Ballistics%20as%20viewed%20in%20a%20morgue.htm
Good comparison article of two of the most revered handgun cartridges of the 20th Century (and still top notch choices here in the 21st); .357 Magnum vs .45 ACP: http://www.guns.com/2012/01/25/the-357-magnum-versus-the-45-acp/
Also be sure to check out Hickok45's channel on YouTube: http://www.youtube.com/user/hickok45
Hickok45 is a great guy with a very nice personality and is very knowledgeable on firearms.
Good luck! Shoot safely, responsibly, and have fun! Life's good! :)