Originally posted by WMBP ... does it make more sense for someone like myself to be spending money on glass or money on cameras?
The conventional wisdom is the good glass will get you further than a good body.
To answer the question in the context of the K100D/K10D, we really need a little more data. DPReview's review of the K10D, the first I have seen, suggests that JPGs produced in the camera are slightly soft and somewhat lacking in dynamic range. To get the best results, you would have to either shoot RAW or post-process. If you are not willing to do either, present indications are that you would not be using the K10D to best advantage, and your money might better be spent on lenses.
However, DPR's assessment of the K10D is disputed by many Pentax owners, and it will be interesting to see whether other reviewers, especially imaging-resource.com, find the same set of issues. If you are willing to shoot RAW, or if other reviewers disagree with DPR, or if Pentax produces a firmware update which addresses DPR's objections, the K10D would be more attractive. FWIW, I have the K100D and am saving for lenses, not the K10D.
Regardless lenses, I have the 50-200, the Sigma 18-125, and recently purchased a used Sigma 28mm F2.8 prime. At 28mm, the Sigma is clearly the best lens I have for image quality. It is very bright, capturing dark detail which the 18-125 would miss. It is noticeably sharper than the 18-125. The brightness has disadvantages, because colors are less rich in good light, especially at long range, and the depth of focus is really thin. Accurate focus is essential. But when the focus is right, the lens produces an image which is lighter, crisper than any other lens I have.
So I'm definitely seeing that primes produce better images. This doesn't necessarily mean expensive primes; my 28mm was under $30 on eBay. Would the $800 31mm limited produce a picture which is $770 better than my 28mm? At my level of photography skill, I'm inclined to doubt it, but like you I'm very interested in seeing comparison shots.
--Brett