Attached Link: www.eovia.com/products/hexagon/hexagon2

I would buy Hexagon and leave Carrara for shading (or work on the shading) and rendering. Especially Hexagon 2 looks to be one of the best choices. Though I still use the spline modeller for simple extrusions from logo's etc. Hexagon 2 will add nice tools for painting (bumps, normal maps, geometry) that will make the combination even stronger.