Thorsten, you might try one of the older versions of IMSI TurboCad or Punch ViaCad, both available from
www.nothingbutsoftware.com. They have TurboCad v. 15 for $14.95 US, and the latest (v. 19) for $120; I've got an older version, and it is in line with your specifications. I haven't used ViaCad, but the product description looks promising. If you're interested in 3d modeling, you might check out Daz3D.com, which is offering their modeling and rendering programs (Hexagon and Bryce) as free downloads. I realize they are not really what you are looking for, as they are not CAD based, but the price is right.