Bottleneck vs Lower Performance: Your CPU won't exactly "bottleneck" any games (i.e. when a GTX660 and GTX670 give the EXACT same performance due to the CPU bottleneck) you can get a lower frame rate than a better CPU and identical graphics card, especially compared to a quad-core i5-3570K, overclocked, in a game like StarCraft 2 which can be CPU intensive.
There's nothing wrong with the card you chose, especially with the free games.
RAM: It's not critical, but if you can increase your RAM it would help in some cases. 8GB is standard for gamers. I wouldn't recommend it if it wasn't so cheap.
If you have 2x2GB with two extra slots, perhaps buy two more sticks of IDENTICAL RAM. Again, not a big deal.
Feel free to ask ANYTHING related to computers or gaming.