Forget Sonnar designs and look at Planar designs...they are sharpest across the plane of the image...but they are also much more expensive than other designs. If you decide on a Contax body, go with Zeiss glass...recognized for its edge microcontrast. My experience with a Zeiss 50/1.7 Planar on film was that the images were crisper than many other similar aperture lenses on film...but that sharpness and microcontrast were less evident at 1.7 than from 2.0 onward. This was true for both near objects such as portraits as well as objects near infinity. The new Planar-50 for certain digital bodies is said to be spectacular, but heavy and expensive. I'd suggest a lot of research on your part, given your particular specs, before parting with your money. You probably know by now, that although your specific requirements aren't mutually exclusive, they may be difficult to achieve in your price range, and flexibility on your part may well result in a satisifying compromise.