Be aware that DXO claims they can achieve the best results by performing the noise reduction during RAW processing, and they have included methods for doing so in DXO Optics.
I've never been able to get that to work very well though in 4.X versions. Whenever I apply the noise reduction tools in DXO, I get artifacts that I really don't like. They're claiming a completely overhauled noise process is included in version 5, to be released any day now.
If that works as advertised, then maybe I'll think differently. But for now, I get my best results with Neat Image in Photoshop, regardless of where I process the RAW files.