I recently picked up photography a bit more seriously again having used Nikon Capture NX 2 for years. I tried all the linux and FOSS options but I ended up buying DXO Photolab 7 and found it far superior for my needs. I've had to setup a dual boot system to get it to work but it's definitely worth it. Dark table is good, but it's a long way off the commercial offerings in terms of ease of use and image quality.
Have you tried the "Denoise (profiled)" feature? It applies auto de-noising per your camera model and metadata quite nicely. You can then fine tune it after enabling the feature.
I've found the profiled noise reduction in Darkroom to do what I need. I've not noticed any significant difference between it and the results I was getting from Lightroom.