Two monitors and graphic card set up

Hi

I need some help. I have two flat monitors on order from Dell (they were
cheap via work) so I need to get a graphic card for dual monitors.

I have a Dell Dimension 8200 P4 2.4 1GB Ram AGPx4 and 400FSB and I am
running a GeForce 3 Ti 500 64mb. FS2004 is OK but gets a bit clonky round
the airports with PMDG737 running.

What I need is the best Graphic card for my system - ie I can get an ATI
Radeon X800 XTPE 256mb, but I suspect I will be saddling a great card with
an average system by todays standards - or am I wrong?.

Any thoughts would be welcome

Stephen