Dual display possible on iMac?

[Island Roots]

I have the first generation of aluminum iMacs, a 20" Intel Core 2 Duo (August 2007) with the baseline graphics card (128MB ATI Radeon HD 2400).

Would my performance suffer if I attached an external display (probably another 20" display)? Does my graphics card have the extra power to run the display? Thanks.

 

[TrapOx]

It would slow down the performance but it will work fine.