Its probably using SLI, links both cards together, to Theoretically double the performance... however when it comes to gaming, SLI usually only generates 30-50% more performance over a single card solution, sometimes less, depending on the games & graphics settings etc.
not sure how the performance gain in SLI is with Quadro Cards & related software, but the software would have to support that to take advantage of it... I would imagine performance gains should be better, especially if both GPU's are used for hardware Rendering.
if its for static images & rendering, usually a better CPU will benefit you more there, or at least the few programs I've used, seems to be the thing. for animations & advanced lighting/special effects I'm pretty sure GPU's will help out even more.
what kind of work are you doing with the programs?
the Quadro FX 1700's are based on the same core as the Geforce 8600GT/GTS cards, to give an idea of performance levels.
depending on cost, would see if possible to upgrade to a single Quadro card based on Geforce 8800 series, or chip/card is based on G80 or G92 core. which would be an FX3700, FX4600 or FX5600, though pretty sure those will be insanely high priced, so might be cheaper to get 2 FX1700's.
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