If you wanna new GFX card within 25k then no look no further go for XFX Gforce 7800GTX or Leadtek 7800GT, its price in kolkata is round about Rs.21,990.
See SLi works for Nvidia cards and Crossfire is for ATI cards, its who have to decide which card you wanna go for, based on that you can buy a SLi or Crossfire config.
But remember to setup SLi config you have to have two identical SLi GFX cards whereas in Crossfire you can setup with any two cards which supports Crossfire.
Regards,
Shovik.