Thanks for all your help guys, very much appreciated. So as I understand it, if I decide not to purchase an exact same model of existing card, I should at least ensure its from the same manufacturer (in my case Nvidia). I am not going down the route of a USB adapter, although I see their uses, so I think its best to pick up a cheap nvidia PCIe card and chuck it in and see what happens, remembering I am only hooking up an old 15inch TFT which I will just use for displaying my email. If no joy with this then I like the idea of a quad head card.
Just to throw a spanner in the works... you have a nice card at the minute. If you are lucky, you may be able to get an nVidia NVS490 or something cheap from ICT Direct (from a similar age XW workstation) so at least you won't be dropping too much in graphics power. If you are really lucky they may have an exact match for your existing card.
Originally Posted by EssexShep
Be aware that a recent NVidia update has been compromised with a zero day exploit
Nvidia Display Driver Service Attack Escalates Privileges on Windows Machines | threatpost
Also the latest NVidia driver update completely broke my existing USB monitor displaylink drivers and IE9 (kept crashing IE on exit).
I have several USB VGA adapters and not had a problem when used for general office apps, but dedicated GPU is the way to go just not sure if NVidia is the preferred choice.