The R7 250 doesn't use a bridge to crossfire, it's done through the pcie slot. The only benefit to that setup is the crossfire will use the 250 as primary card, so uses the gpus dram vrs the system ram used by the APU. Less stress on the APU, lower temps. Being crossfire though does have disadvantages, such as dismal support in many games. Making it almost pointless at that power level.