If you have pdms installed on your system you can view it from the installation guide and better still you can view this link for current list of supported graphics card. http://www.aveva.com/products/support/support.html
Quadro FX is the standard defined by AVEVA, within our company we use a variety from the entry level fx540, mid range 1500 and the high end users use the fx3500.
the entry level card suffers slow down on complex plants, on very large plants it becomes almost unworkable, but is capable of handling single lift modules.
the 1500 handles most PDMS Design work without issue, while the fx3500 allows fully rendered walkthroughs to be seemlessly presented for presentation avi's etc which can suffer a little slowdown using a 1500.
Hope this is of help, you could always go for the dual card 4600/5600 setup of which we have no experience but if money was no object, why not!
we have been using Nvidia Quadro Fx 3800 with 4 GB Ram on a machine but facing error while opening two models of 1Gb each together.
We can open the models seperately but when we combinedly open the models, it shows the memory corrupt or reading file error.
Please advise. It's urgent.