Thats not fair....neither of those are even close to the $650 body/lens combo price of the Pentax. They are shooting for different markets.
I'm not sure what this has to do with "fair". ISO 1600 is ISO 1600. The point is that at that moderate ISO level the noise reduction is extreme, to the point that it's killing the red channel. At ISO 800 the details are there, see below.
The solution I would image is to shoot in RAW and do your own selective noise reduction. It's not a condemnation of K-X, it's just an observation. It was brought up when skid mentioned the high ISO performance being outstanding.