I actually just ordered the Scythe Ultra Kaze 38mm with the heatsink today. So if you you can wait a few days, I'll let you know how it does. I'm guessing it will be more than enough. I've seen a lot of other people have used very similar 25mm fans and have had a lot of success.
The 38mm Scythe fans I ordered were too big so I ended up using the scythe slipstream 25mm 1900 RPM fans I had also ordered. It has been performing very well at a high overclock and I highly recommend them. If you order a fan controller, make sure it does more than 6w per channel.