6W per channel = 0.5A
Even the 1,850RPM Scythe Gentle typhoon only requires 0.083A.
The Noctua NF-P12 1,300RPM only requires 0.09A.
As long as you're not using something like the fast Yate Loon fans (0.7A) then you'll be OK.
If you can say what fans you'll be connecting you'll get a better answer.
It's the three stock fans that come with the CM 690II case (not sure that amperage), a BitFenix and a Yate Loon with 0.06 and 0.3 respectively. My two Noctua fans aren't too noisy with the Ultra low noise adapter, but i may add them any way.
It looks like that fan controller will work fine then if it's the one you want.
Do all the fans have the 3/4 pin fan connector?
If any are just molex powered then you'll need adapters to use them with the fan controller.