Does any one know of a guide to choosing a graphics card?

[David Franklin]

when funds allow I intend to add a Del 30 inch (2,560x1,600) monitor

But I cannot work out if the HD 4670 will work on this

Nor can I, not with any degree of certainty (note that Laptop versions of cards are often specced differently from mainstream versions, so just checking reviews of the card isn't really enough).

For that amount of money, I would ring up and ask. If they can't tell you, that tells you something about the company you are dealing with (and will have to go back to if you have any problems).