personally if pentax made an equivalent to the a900 I'd preorder, but in regards to your image. looking at dynamic range on dpr (so maybe I reading things wrong and doing something stupid
but the k20d outperforms most of ff's at iso100
Camera (ISO 100) Shadow range Highlight range Usable range
Pentax K20D -5.8 EV 3.2 EV 9.0 EV
Canon EOS 450D -5.1 EV 3.6 EV 8.7 EV
Sony DSLR-A700 (ISO 200) -4.9 EV 3.9 EV 8.8 EV
Olympus E-3 -5.8 EV 3.0 EV 8.8 EV
Pentax K10D -4.5 EV 2.8 EV 7.3 EV
Nikon D700 (ISO 200) -4.4 EV 3.4 EV 7.8 EV
Sony DSLR-A900 (ISO 200) -5.1 EV 4.2 EV 9.4 EV
Canon EOS 5D (ISO 100) -4.7 EV 3.5 EV 8.2 EV
Nikon D300 (ISO 200) -4.7 EV 4.1 EV 8.8 EV
Nikon D3 (ISO 200) -4.7 EV 3.9 EV 8.6 EV
+ there is k20d's drange feature to give an extra stop (and noise), personally I'd bracket and transpose sky from other shot, but it increases work.
Phil