Get two Enermax Magmas for those extra 120mm slots. I don't have experience with Rosewill fans, but I doubt they are better/quieter than the best fans on the market today. If you have the money, then go for better ones. You can't go wrong with Noctua, Sycthe or the superb Noiseblockers.
Before purchasing replacement or additional fans see what happens with stock cooling. There are several free utilities which can measure cpu and gpu temperatures. If cooling is satisfactory there is no need to anything. If cooling is not satisfactory, then you can think about replacing the stock fans and adding more fans.
Just about everyone has their own personal favorite fans. I've had excellent results with Scythe S-flex 1600rpm fans:
Thanks for the help! So I guess I will definitely want to start out slow and get at least one good fan. The question now is, get 1 good fan and then keep the stock fans and see how that goes, or should i just bite the bullet and replace both stock fans and get a third good fan as well? I want to make sure I'm doing things right. No use spending all this money only to cheat on the fans. Also, should i try to set the case up for positive internal pressure?
If you can afford, replace them all together There's no need to wait and see, you will have better perfomance and less noise if you upgrade all of them, there is no doubt as I did the same last week and lowered around 5C average with almost no noise at all. And yes, positive pressure is better...