IMO, if one really wants to compare IQ at high ISO between K-x and K-7, I'll say this... forget it la. Haha..
Whatever you got in your hands (be it K-x or K-7) is something that will give you pleasant memories of precious moments. That is the truth.
I remember the days when I was still using film cameras, had so much fun with it. Sometimes I got blurr subjects but still the moments were captured and it was worth keeping. Now comes the digital age and people are too concern but specs, specs and more specs (i'm guilty too). Let's just go back to the old mindset, shall we?
Have a great weekend.