Dual card or not?

[omechengineeru]

Ok so i just built my new computer b/c my last one was old and finally died. Then bfg did the promotion were they were doing the free agp to pcie upgrades, so i got a brand new 9200 gtx. The question is, should i put this in my new computer to use dual monitors or just dual through my 280? What would the difference be? Otherwise i'm just going to use it to piece together a computer for my mom.