Dell PC with 4 monitors

Hi,

I need to purchase a pc for work .

I would like to have 4 monitors.

I don't play 3D games in work :)

but I am running application like LabVIEW that needs some graphics abilities.

however, not more than a regular pc.

I would  like to know which of Dells pc's are supporting SLI or Crossfire.

does the pc comes with one video cards ?

e.g. DELL PRESICION T1650, is he enough ?

what video cards can I buy, and why they all cost so much ?

can you give me recommendation how to choose the Dell Desktop computer ?