Ati 2600 Xt V 1950 Xt

Hi, I have just replaced my sapphire 1950 xt with a Sapphire 2600XT 256MB GDDR4 Dual DVI-I TVOut PCI-E Graphics Card, I thought I was upgrading, but the 1950 was much better, will I get a significant performance boost if I twin it with another 2600 xt I have crossfire support, or would I be better off selling it and getting a 2900 xt, my mobo is asus P5W-DH DELUXE, ANTEC TRUE POWER 550 WATT, INTAL QUAD CORE and 2 gig of crucial 8500,

You can see what the differences between the two are on this page
http://www.gpureview.com/show_cards....=467&card2=520