You spotted correctly that after so many years, few sub-$500 cameras can beat F31 in high ISO performance although F200EXR is quite close. Hope you don't bring in those models resorting to blantant noise suppression at expense of resolution like S90 here. On the same token now, few sub-$500 cameras can get close to F200EXR for dynamic range. Perhaps, you might want to name us if there is one.
Like many others, I was also initially misled by the large sensor and fixed lens design thinking DP-2 must be among the best PnS. It is true that sensor of DP-2 is far bigger than F200EXR. But I suspect resolution of large CMOS may not necessary be comparable to smaller CCD if dkcamera is correct. Also I am not sure if Sigma is known for highest quality optics though its F2.8 lens is fixed (but certainly better than S90's tiny elements F2.0). Have you not seen enough poor pictures taken from 35mm film which is even bigger than DP-2's sensor?
Maybe it is interesting to read a rather unsubstantiated suggestion against dkcamera. I also don't read German but I know it is a language used often by people who might be more careful and thorough than some. You might want to know other than dkcamera, the large sensor of DP-2 also didn't show up too well with the 1/1.7" sensor of Ricoh GRD III
http://www.dpreview.com/reviews/sigmadp2/page21.asp. Unfortunately doreview have not included 1/1.6" sensor of F200EXR in the comparison.
Come to think of it, choosing a PnS camera can be confusing now like what you say, particularly when brands are offering meaninglessly high pixels, high ISO with blurred image, using big aperture with little glasses, lavishing on full page advertisement, hiring professionals to advocate, sometimes even including seemingly larger sensor, inadequate consideration for quality optics and what have you.
I'm a little confused. Comparing DP-2 with F200? The DP2 sensor is at least 7 times larger than the Fuji. I'm beginning to think the dkcamera test is flawed in some way. I can't navigate in the site cos I don't understand German. I think we're getting ahead of ourselves here. To put things in perspective, at ISO800
The F200 can't even compare with the F31!
Which is good for me cos i just got the latter for $200 used