OMG, I haven't messed with a Tornado in ages. They are so damn noisy!
If I were you, I would regroup and spend a little more money, not on a fan controler, but rather on a new heatsink and a dremel tool. First, I would replace that stock cooler and that duct looking thing and replace the heatsink with a
Cogage True Spirit. That will lower the temps on that hot running 920 in your system. Now for the Dremel part. Buy yourself a Dremel tool or a metal nibbler and cut that incredibly restrictive stamped grill out of the back side of the case, leaving the screw tabs for mounting the fan of course. Then, to keep the fingers out of the fan, get yourself a
92mm fan grille to put on that fan, which is much less restrictive. And then use a regular speed 92mm fan instead of that Tornado on the case. You can also do the same case mod for the front intake fan too and since it's behind the front face plate a fan grille isn't necessary. Cutting those "cheese grater" stamped grills out of your case is one of the cheapest and easiest mods to do to a case to improve airflow and lower noise levels. And leave the Tornado on the desk to impress people with and dont try to use the noisy bugger, as even on a fan controller and with the speeds cranked way down they still are noisier than a regular case fan.