Best Graphics Card For My Setup

I was hoping someone could answer my question regarding GeForce Graphics vs Quadro FX graphics. I have a custom computer built from Rain Computers (all the specs listed below) that currently uses the Quadro FX 3800 graphics card. I use the computer a lot for HD video editing and will soon be purchasing Toon Boom Harmony Standalone. They have told me that the GeForce Graphics card would better support their program, however, I have been told elsewhere that Quadro is very solid for video editing. Is the GeForce a better card overall, or is this like comparing apples and oranges. I would like to invest in the best graphics card that my current setup can offer, as I want the smoothest rendering and real-time playback as possible. Specs below, thanks for your help.

Intel Motherboard Dual Socket Xeon S5520SC
Intel Xeon CPU Fan Heatsink STS100C
2 x 2.26GHz Intel “Nehalem” Xeon Quad Core [8MB]
12GB 1333MHz DDR3 Triple Channel SDRAM (6 x 2GB)
1TB High Speed Hard Drive [64MB Cache, 7200RPM]
StormDrive Dual Layer CD/DVD Writer
850W Silent Power Supply
Windows 7 Pro [64-bit]
NVIDIA Quadro FX 3800 Workstation Graphics Accelerator [1GB]
PCI 3 Port FireWire [TI Chipset]
(additional) 1TB High Performance Drive [64MB Cache SATA 3 6GB]

First, possibly a dumb question: what exactly is OpenGL?

Second, the quadro works very well for my Adobe CS5 setup. Ideally, i would like to lose little (if any) quality there. So i’d like to find a card that’d suit both the needs of HD footage in CS5, and the work I will do in Harmony.