Noctua 800Rpm 8dBA vs 1200Rpm 17dBA for Antec P182 SE

Hola Mates,  

I have Antec P182 SE, with its original 3 Antec TriCool fans (always on Low speed).

This is my system:

Case: ANTEC P182 SE Aluminium
CPU Cooler: Thermaltake Big Typhoon VX CL-P0310
Power: Corsair 520W 40A @ 12V CMPSU-520HXEU EPS 12V Modular
CPU: Intel Core 2 Quad Q6600 2.40Ghz 8MB Conroe -=Stepping G0=- OEM
Graphic Card: Sparkle 8800GTS 640MB Retail
Sound Card: Creative X-Fi FATAL1TY Pro SCXFIFATP
Hard Drive: Western Digital 500Gb 16MB WD5000AAKS x 2
Motherboard: Gigabyte GA-P35-DS4 Conroe Support GP35DS4
DVD Writer: Samsung DVD-RW S183L X18 LightScribe SATA
Memory: Corsair 2GB Kit (1GBX2) XMS2 DDR2-800 CL4-4-4-12 6400C4

I am thinking of adding a 120mm case fan for the middle cage (where you can put hard drives as well).



For now, I am not sure if I'll replace all 3 TriCool fans.
Maybe in some months from today.

I don't know if to take Noctua 120MM Case Fan NF-S12-1200Rpm 17dBA or Noctua 120MM Case Fan NF-S12-800Rpm 8dBA.

1) Should I add to the case Noctua 800Rpm 8dBA or 1200Rpm 17dBA?

2) Less Rpm for less noise OR more noise for more Rpm?

3) Do you think, that the Noctua fan is gonna be productive & effective in this location?


Thank You Very Much for your help!