Worth upgrading my video cards for this resolution

I'm currently using the following-

E8400 o.c. to 3.5Ghz
4Gb 800Mhz (roughly at 940Mhz) G.Skill ddr2
Asrock Penryn 1600sli-110db motherboard
2x8800gt sli running at 700Mhz core
H.P. w1907 19" monitor (1440x900)
Seagate Barracuda 500GB hd
Dual boot XP 64-bit and Vista 32-bit


Is it worth selling of these cards and getting the 4850x2 or 4870x2 at the res. I'm playing at? I dont plan on upgrading my monitor for at least another year. Any opinions are welcome.