I would get the drp4 cause the noctua is ugly and you have a be quiet case. For case fans I would also go with the 140mm sw3 pwm, I think your case comes with pw2 fans which are fine but the sw3 are better, not sure I would upgrade the stock fans maybe just add 1 more to the front.
edit: part of the reason the sw3 are slightly better than the stock pw2 are that they come with anti vibration mounts while the pw2 is just hard plastic with screws, if you get 8 anti vibration mounts like the noctua ones you will improve the performance to noise ratio of the pw2 fans.
In summary I would keep your current case fans and add another 140mm sw3 fan to the front and remount your current fans with anti vibration mounts.