this will include all that you need to build a system. Like GeekApproved said though, this is kind of a low end gaming rig. $550 makes it hard, but for this price, there is a lot of muscle. Lag is a term for internet connections, FPS is what your gpu will put out. i run a 560 OC'd to 950MHz, and it runs like a champ. for a "mid-ranged" card, it rocks. so, the 550ti was more of a budget buy for you, but should perform well enough for you to get what you need out of it. Also, if you are planning on OC'ing the cpu, watch your temps and run Prime95. the stock cooler is a beast comparitively, but it is still a "stock" cooler. If you have patience, i would wait it out though. for another $150 in your budget, you can make some serious upgrades to your video card, and possibly even your mobo for future upgrades.
All in all, this setup will get you where you want to go TODAY...1yr from now, you may be upset with your computer's performance though. The choice is yours, Best of Luck!