As you are in Europe, I would strongly recommend the Retina IIc with Rodenstock Heligon 2,8/50.

I have found the Heligon 2,8/50 to be sharper than the Schneider Xenon and the 2/50 Heligon on the IIIc. I've had a couple of Retinas with these lenses and always found that the 2,8 Heligon is the sharpest.

My favorite Retinas at the moment are the IIc and Ib (with 2,8/50 Xenar, but without rangefinder).