WH!ch VIDEO CARD for MP 1,1 ( 2,1 Flashed )

Hi all

Which Video CArd for an Mac Pro 1.1 ( 2.1 tiamo ) ? normally update to ELCAPITAN

I have Actually ATI 4870 1giga , i want replace this last one for more power

Do you have some cards recommandations ?

Thanks for your help

Girafe