I've been using this technique for a while now, though using Nik Dfine instead of Topaz denoise, especially on night aerial images. The technique was thought up by a 17yr old (at the time of posting; it's been published a while) Brazilian K3 shooter. It allows a lot of sharpening without any increase in noise. Worth a look.
http://blog.topazlabs.com/tutorials/ima ... 03714689cb