I get good files up to 6400, to the point where I consider digital grain adds texture and does not detract from detail and the image quality. When it starts to detract from the image quality then IMHO it becomes noise.
I don't think I've particularly low standards either saying that. Though I should mention that I have come from film, so I actually find overly clean files to look sterile and unattractive. I feel many people today obsess with noise when the reality is digital 'noise' of yesteryear (with it's banding in the shadows
) has become a thing of the past. Todays grain at higher ISO's is much finer and random in nature - dare I say it - much more film like.. I actually add grain in for most of my digital workflow in post with the EM1.
If I absolutely must nuke all semblance of grain, I use DXO Prime noise reduction technology. This is amazing, but the default Olympus settings are far too aggressive. If you go the DXO route I suggest that you half the default value of '40' and goto a luminence noise value of about 20-25 for ISO6400 images. You will only see the benefit in the actual output file or the small sample window above the slider, so don't base your opinion on the main view window
On an aside ...
Check out this guys work
http://www.stevehuffphoto.com/2014/03/21/a-night-at-the-opera-with-the-leica-monochrom-m2/
The monochrom with it's much much cleaner files do not look as subjectively attractive to me as the M2 with Ilford HP5+ film. A modern OMD will produce files that are much cleaner again than this at a much higher ISO.
It could just be that you just don't like the 'look' that this format provides. If that's the case, no harm, maybe it's time to jump ship to a small format digital like a 5d mkiii , 6d, d800 etc... that gives you what YOU want. It's your hard earned money, you don't have to justify it to anybody