Studio XPS 435 MT - replacing graphics card

Good Morning,

I need to replace my original ATI Radeon 4800 card with something newer, because the current card is on its way out (overheats and then computer blue screens etc)

It's got an i7 940@ 2.93ghz and 8gb of RAM

Can anyway recommend a new card ? I don't want to spend too much on this.

Thanks for any help

Ade