For professional users

Quadro FX 4600 - 8800GTS PCB, 768MB GDDR-3, 384-bit, bandwidth of 57.6 GB/s, clock 1.2 GHz.
Quadro FX 5600 - 8800GTX PCB, 1.5GB video memory, clock at 1.6GHz.

http://www.theinquirer.net/default.aspx?article=38041