Yeh this is a good idea. I am actually going to be doing this to my pre cooler soon. Only I will be using 140mm fans. The pre cooler alone has made a drastic improvement to the temp of my water. The fact that I am running a gt30 turbo was enough to want to get the temps down as it does like to kick out some serious heat.

I also bought the new slimline fan kit from Auto Specialists. I was sick and tired of the noise of the original fans when they came on. They are pricey but definately a great upgrade.