For CAD applications a professional grade GPU (e.g. NVIDIA Quadro®) will give you cleaner detail on your models than a standard or gaming GPU. Also panning, zooming, rotating your model will maintain better visual integrity with a GPU designed for 3D CAD applications. Getting into the cost differences between lower and higher end professional grade GPUs you will need to determine your actual requirements. For the majority of engineering applications you should not need anything more than a mid-level professional GPU (e.g. NVIDIA Quadro® FX 1800). Unless you do a lot of rendering and need photo-quality images for various reasons the higher end GPUs won't make a lot of difference on performance. If you're doing more engineering analysis I'd recommend going with mid-grade GPU and putting extra cash into CPU, hard drives, and RAM. Just my 2 cents worth, oh, and I'm just using NVIDIA as an example, our workstations utilize both NVIDIA QuadroFireProTM and ATI Fire GPUs. Hope this helps.