Temperature controlled fan in PSU, where should thermistor go?

[J3anyus]

I'm thinking about changing the noisy fan in my 400W Sparkle to one of those Enermax thermal controlled fans. However, I have no idea where I should place the thermistor. If I put it on the heatsinks in the PSU, it'll probably be at its max noise and CFM all the time, but if I don't put it in the right place, the PSU might overheat. Any suggestions on where I should put it?

You can get an idea of the inside of the PSU Here.

Thanks,
J3

Edit: Specifically, I'm looking at putting in this fan.

 

[SilversinkSam]

I have a similiar fan in Enermax PSU and I put the temp sensor taped to the top of my primary hardrive, I also tried in between my heatsink 'vanes' close to the base of the heatsink.

 

[Insidious]

I'd try at the air inlet to the PSU. If your fan doesn't run hard enough, try the air outlet from the PSU.

 

[gkwok]

I have the very same fan that I replaced in my Enermax 350W power supply. I used tie-wraps to position the thermisistor close to but not touching the large heat sinks in my power supply, being careful to keep it out the airflow of the 92mm intake fan and the 80mm exhaust fan. The fan spins at between 1600-1700rpm.