did you get the 120x92 SilenX fans?

Those fans look like they would be quiet, but at the same time they only push 72 cfm (cubic feet of air per minute).  For comparison, the Silverstone FM121 fan that I mounted on my Corsair H50 pushes 110 cfm at max speed.  Your case may be heating up from either low airflow, or you need to work on your intake/exhaust air flow ratio in your case.

You would get better results for physx if you use one of the 480s instead of the CPU. GPUs process physx much more efficiently than  CPUs do. Still you really need to improve your cooling, as others have stated. 90 to 100 degrees is very hot. Cable management can help with air restrictions as well.

Yea it can be hard to deal with all those cables. The case you have is a pretty good one. I think if you keep playing around with your fan placement/ configuration better results can be achieved. You might try resetting the fan profile as well. 480s are hot running cards by nature. They are obviously capable of surviving high temp. I noticed from your sig. that your hitting these temp. while running stock clocks. Doesnt give much room for OC. The block you linked to would work perfectly fine on a gtx480. However I dont think you would want to liquid cool just one card in an SLI config. I am by no means as smart as most members on here , but I am happy to try and help.

There should be plenty of room in your case for a liquid cooling system. It is not overly dificult to do. You just have to take your time and follow the manufacturers instructions when installing the blocks. Yes you have to disassemble the cards and remove the fan and cooler. Keep in mind that you will need (This is by no means all conclusive) a pump, reservoir, radiator, tubing, various fittings, coolant, as well as the two GPU water blocks to complete the system. As you can see it can be quite involving and can get expensive. I think I spent between 400.00 and 500.00 on mine. My system is far from top of the line, but I am very happy with the results. The first place I would start would be right here on these forums. Look at some of the Mod Rigs members have put together. Also; Youtube has some really nice videos on block and cooling systems installations. Do some research and decide if you really want to attempt such an endeavor.  Again I am not as knowledgeable as a lot of the members here. I do have a pretty good grasp on the fundamentals involved though. Hope this helps some. 

Your welcome. Glad I could shed some light on the subject.