FireUser.com has a user-contribution from Antonio Fontenele benchmarking a Quadro 1800FX against the AMD FirePro v5800 in a variety of tests.  In an interesting twist he compares the various vendor “optimized” drivers against their counterparts provided by Autodesk (Both of these cards are Autodesk approved), and finds a startling different in performance.

In Cadalyst Systems Benchmark 2011 test, Quadro a little faster than FirePro while using AutoCAD default drivers due c2011_8.dwg file score, but it was slower than FirePro in the other files (where FirePro was 102.32% faster). However, using AutoCAD optimized drivers, Quadro earned 613 points while FirePro earned a higher score equal to 2060 points. This is means about 336.05% faster in AutoCAD 2011.

Get all the numbers in the article.

Performance Comparison in AutoCAD between NVIDIA Quadro FX 1800 and AMD FirePro V5800 | FireUser Blog.