What is the best graphics card for FCPX?

In the nonstop anti-FCPX propaganda is an article of interest — posted 7/9/12 — comparing the benchmarks of FCPX and PP6.

http://www.streamingmedia.com/Producer/Articles/ReadArticle.aspx?ArticleID=83582 &PageNum=1

The system used was a 2 x 2.93 GHz Quad-Core Mac Pro from early 2009 running MacOS X version 10.7.4 with 12 GB of RAM and an NVIDIA Quadro FX 4800 graphics card with 1.5 GB of onboard RAM.

In most cases PP6 outperformed FCPX with this configuration. However, in the comments Ben Balser pointed out that FCP X's A/VFoundation engine wasn't ideal on the NVIDA card:

"Quadro is actually not the best card for FCP X's A/VFoundation engine, but great for CS6's Mercury engine, so the test is amazingly flawed right there. Try both on a 5780 card and watch things drastically change. I've done that test myself. Exporting to Compressor uses a MUCH more sophisticated encoding engine meant for higher level, professional transcoding, not simple outputs, which are faster using Export Media…"

Apple lists this card on its support page: http://support.apple.com/kb/HT4664

So,

What is the best graphics card for FCPX?