Here's something worth reading re 30 bit colour depth and support..........
Some newer graphics cards support 30-bit RGB and higher. Its color palette contains 10243 = 1,073,741,824 colors. However, there are few operating systems nor applications that support this mode yet. For some people, it may be hard to distinguish between higher color pallets than 24-bit color offers. However, the range of luminance, or grey scale, offered in a 30-bit color system would have 1,024 levels of luminance rather than the 256 of the common standard 24-bit, which the human eye notices more than what hue a colour is.
The Quadro FX 4800 and the Quadro CX is a fine card series for this sort of work but comes with a fine price tag as well.....Cuda cores are were most of the performance will come from for what your doing......a fair bit of research will be needed to target exactly what you need which will save you fun tickets in the long run!
Aussie Allan