Impossible to improve IQ in post?

So I finally got Lightroom 4.

I shot some night shots with my newly arrived Epl-5. The good news is I am very pleased with the amount of light hitting the sensor with a combination of the 45mm 1.8 and a 1/15 shutter speed which seemed to give consistently sharp results with the IBIS. At 1600 - 6400 you can really get a well exposed image even in dark conditions - this means I likely will forget about the Fuji X-E1.

The bad news is I could not improve the level of detail in 100% crops in Lightroom. Do you guys agree that this is impossible to do?

Using noise reduction just creates awful water color effect which may reduce some noise, but takes away detail. I prefer the noisier look with more detail.

Increasing sharpness only seemed to create more contrast I would say.

So is it unrealistic to think that we can truly improve IQ in post?

(Now, if we are talking about smaller sized, fine, I think there can be a perceived increase in IQ, because you don't notice the smearing or lack of fine detail that is introduced.)

What do you guys think?