These are the best cards for solidworks in order of your price range:
1. Newegg.com - PNY VCQFX580-PCIE-PB Quadro FX580 512MB 128-bit GDDR3 PCI Express 2.0 x16 Workstation Video Card - Workstation Graphics / Video Cards
184.99 (cheaper somewhere else than newegg)
2. Newegg.com - PNY VCQFX1800-PCIE-PB Quadro FX1800 768MB 192-bit GDDR3 PCI Express 2.0 x16 Workstation Video Card - Workstation Graphics / Video Cards
3. Newegg.com - PNY VCQFX3800-PCIE-PB Quadro FX3800 1GB 256-bit GDDR3 PCI Express 2.0 x16 SLI Supported Workstation Video Card - Workstation Graphics / Video Cards
Benchmarks from sites like Tom's Hardware show that Nvidia is superior for solidworks
Charts, benchmarks Workstation Graphics Charts, SPECapc Solidworks 2007 Graphics
The FX580 benchmarks are close enough to the other two quadro cards that it'd be tough to justify the extra price for the other two.
Other programs like unigraphics and proE favor some other cards - its a tossup.
If you havent even gone into CAD programs yet I'd go with the FX580, and upgrade in a few years when you'll be dealing with the complex modeling that would require a higher level card.
You'll find most companies are using solidworks now. Solidworks is owned by Dessault Systems - they also make Catia. BMW uses
Pro/E is a dying CAD program in my opinion. Unigraphics or siemens NX has very limited applications. Inventor, while good from what I've heard, just does not have as much exposure in the world as Solidworks.
I wouldnt bother with softmodding ATI cards to their FireGl equivalents. I have yet to see anyone do it with awesome results as far as CAD applications. Read into it more here: nVIDIA Geforce 285 260 9800 275 295 GT GTX AMD ATI Radeon HD 4850 4870 4890 X2 - Guru of 3D: PC Hardware Reviews