Hmmm....A 92mm on an SK7? I'm not sure if the SK-7, itself, is big enough to hold a 92mm fan. *goes to thermalright site to find out* According to thermalright it's 2mm shorter (in length) than the SLK-800. It should be able to fit if this is the case. You may need to mod the clips a bit to get it on there, but you should be able to get it on. Refer to this:
http://www.angelfire.com/cantina/nerdlogic/bending.html
for clip bending.
I warn you that the Tornados are LOUD. You may say you don't care about noise now, but you will once you have it running for a while and it drives you crazy.
More airflow in your case is beneficial if you don't have enough, meaning that if your case temps are too high above ambient temps, get the air flowing better. IMO, having your airflow balanced is the optimal option. 3 SFIIs will do fine. I would suggest 2 for intake and one for outtake (you'll have the PSU fan to help with the exhaust as well) and you may have slightly positive pressure, but it's pretty hard to achieve a perfect balance. Cooling your northbridge and memory will help your overclock, but will do nothing for your CPU temps. Also, if that's 35°C case/50°C CPU temps, then check a few things:
-Remount the SK-7 and make sure it is making good contact with the CPU.
-Reapply the thermal compound according to
http://www.arcticsilver.com to make sure you have a proper TIM joint.
-Depending on your ambient temps, those 3 SFIIs will most likely help.
-Depending on the base of your HS, lapping it may shave off a few degrees.