No doubt the k-x has a good sensor, but let's not get carried away comparing an entry level DSLR, to pro/am cameras. The pictures you posted are a tiny little sliver from a 100% crop at DPR. The "hair" of a stamp picture is not a really good way of quantifying the amount of detail left. Go to Imaging Resources and look at results from the comparometer. In particular, look at the parts of the picture that includes the "proportional scale" so you can see the remaining resolution and detail. The k-x is at least 2 stops behind the D700 and the 5dMkII.
Still, the k-x is excellent for an entry level camera, but is it really any better than the direct competition? Which is the k-x below, and which is the entry-level Nikon D5000? Both are 100% crop at ISO 6400:
Edit: smc, regarding your question about ISO100, this thread was related to that question:
https://www.pentaxforums.com/forums/pentax-dslr-discussion/86265-k-x-blows-45...omparisin.html
Last edited by PentaxPoke; 01-30-2010 at 02:07 PM.