I shoot the three DPM cameras, the SD1M, and MFD as well. The DPM cameras are my MF in a lightweight shoulder bag. If you can't get all three, I'd start with the DP2M as it has a razor-sharp 30mm f/2.8 lens that is a 45mm f/2.8 equivalent. You might need a loupe for shooting in the sun since there is no EVF. The Sigma optical add-on VF is a waste of money IMO, and I use a Hoodman Loupe and prefer it over the aftermarket EVF I purchased.
As advised above, you should wander over to the 'Other cameras' thread in this forum for advice, questions, and images regarding the Sigma line of cameras.
A few Sigma DPM pictures:
Water Lilies, etc.
Sigma DP2M, 1/50 sec at f/8, ISO 100
St. Marks Lighthouse
Sigma DP1M, 1/1250 @ f/2.8, Handheld
Sigma DP2M, ISO 100 +0.7, handheld
Sigma DP3M, ISO 100, 10 sec @ f/8.0