DXF files including compatible entities (look at the ArchiTerra user manual for further info) with 3D info.
If the levels are simply "written" (I mean the level is showed in a text) or are blocks entities (block are like the AC objects) ArchiTerra cannot import them.
Maybe if you could privately send me this DXF file I can check it and be more useful for you.
Friendly
Fabrizio
Fabrizio Diodati
Graphisoft Italy Srl | Via Rossignago 2/A Spinea Venezia 30038 Italy