Sim, você pode usar o Crossfire. Veja aqui :
A little over three weeks back, AMD unleashed their HD3870 X2 graphics card which put AMD back on top for the fastest graphics card. Although the card featured a Crossfire connector bridge, drivers were not available to take advantage of this feature. AMD has now released their 8.3 Catalyst drivers that allow you to run two HD3870 X2 graphics cards in Crossfire mode allowing you to harness the power of four GPUs.