I have a perspex panel on the side of my case with no hole for a fan. My 2 GTX 580's love to get very hot and the fan at the bottom isn't cutting it. How should I go about cutting the perspex? I don't have a drill as neither my husband or myself are very good at DIY. I really don't want it to look like a rushed job . Any hints or anything else you can suggest to cool down these cards?. They are getting to 90c - 95c during heavy gaming (max settings on Farcry 3). The internal case temp is 24c and the ambient temp in the room is 20c. The CPU reaches a maximum of 70c under load (AIDA 64 stability test.
I have replaced the TIM on them with Artic Silver 5, using a thin layer only. I read that AS5 isn't great because it is capacitive but I made sure to apply it neatly and evenly. There was no over spill. Could this type of TIM be the cause? it's 9.0W/m.k , should I go with something thinner?
Thanks in advance and thank you for the website. I feel more comfortable asking for help on here than on those other forums. Very beginner friendly!.

WATER COOLING IS THE ONLY WAY TO GO !

i have 2x 570 GTX twin frozr III and it doesn't overheat.

My specs

Cooler master sniper
8GB RAM
i5-2500k @ 4.5GHz
2x Geforce GTX570 twin frozr III
Thermalright silver arrow cpu cooler
MSI p67a-GD65

My highest temp is about 71C on Battlefield 3 for 1 hour. I do limit it to 60FPS via vsync. I must admit that my system is running a bit loud but I use headset anyway so not a big problem for me.

I have been doing SLI/Crossfire for years. Get a big case with lots of air moving through it. Then make sure you buy a mobo that has two slots on it minimum between the slots the cards go in. This way you have a one slot gap between cards once installed. That is the cheap and easy option. The better but more expensive, by a large margin is water cooling.

what if 2 cards are very close to each other when running SLI/CF? like on most mobos the distance between 2 cards is 1 PCI slot

A cheaper option might be to replace the case all together and go for a bigger more ventilated one.
If all else fails try the mighty Delta Electronics 120mm fans like the PFB1212UHE for example.

Don't forget spot fans like the antec spot cooling fan

you could also buy a new cooler for your video card something like arctic cooling i got a Hd 4890 with a ARCTIC COOLING Accelero Twin Turbo Pro and its running cold (=

http://www.arctic.ac/en/p/cooling/vga.html