CAD viewer for Mac

I am looking for a viewer for Macintosh OSX 10.7 to open and view .igs, .stp and .dwg.

I have eDrawings from SolidWorks. It will open .dwg and also everything created in SolidWorks that is export as an "eDrawings" format but it will not open .igs and .stp.

I also have TurboCAD for Mac and it's "OK" but it will not always open everything. It's hit or miss. Just wondering if there is anything else out there?

I think with the large numbers of Windows users in the manufacturing, engineering industries, switching over to Mac someone coud sell quite a few seats of a viewer app in the $100 - $200 range. .igs, .stp and .dwg are the most frequently exported from CAD programs such as SolidWorks, AutoCad, Inventor and ProEngineer.

What about TurboCAD?

Key Features

It is $130 but theres a trial there so you could see if it works.

Description shows:

Import or export from these popular formats: 3DS, Adobe® EPS, Adobe® Illustrator (export only), Adobe® Photoshop®, BMP, AutoCAD® DWG/DXF, IGS, JPG, PICT, PNG with alpha channel export, ACIS® SAT, Spline, STL, STEP, TIFF, TEXT, Truespace COB, Claris CAD (import only)

No .stp though