If they're on the appropriate PWM header of your motherboard, you don't need to.
Incidentally, I use a Prolimatech Megahalems CPU cooler coupled with an Apache (or perhaps 2...) 120mm fans. I never hear the CPU. The graphics card is quite noisy, but I don't mind when I'm playing games. I wouldn't recommend a Lian Li case (I have one), it's over-priced, not quiet and not particularly great for cooling either. My old Chieftec Dragon case was superb, but rather out-dated and tired. I've built into a lot of cases, and probably my favourite of recent times was an Antec P180. It was just abotu big enough for a high end rig, almost completely silent, and kept things moderately cool. That rig wasn't for overclocking or gaming, but did require large amounts of CPU power for the work done on it.
Almost no manufacturers provide accurate information about how quiet their cases are (it's not just the fans, JDC, although undoubtedly quiet fans help matters!). This Lian Li I have was marketed as quiet, and it's pretty poor, in my opinion based on very similar (and in one case identical) specced systems being built in other cases. Yes, it's aluminium, but that's a gimmick in most cases - steel works just as well, and yes it does look quite good (less of a gimmick to some), but really that's the only positive thing I can come up with.
I digress...