It is not going to be as powerful as the Radeon HD 7750. All reports I have read regarding the A10-7850k's graphics core states that it would be about 30% - 40% more powerful than the integrated Radoen HD 8650d which is equivalent to the Radeon HD 6670 DDR3 graphics card. The Radeon HD 7750 is beyond 200% more powerful than the Radeon HD 6670 DDR3. What you have probably read is that Kaveri's top of the line graphics core is rumored to have 512 SPs (Streaming Processors) which is equal to the number of SPs found in the Radeon HD 7750.
Additionally, the Radeon HD 7750 uses DDR5 RAM which is much faster (and more expensive) than DDR3 RAM. Right there is likely a 25% performance penalty if not a little more. If the reported 30% - 40% iGPU performance increase over Richland is true then that means Kaveri's iGPU will be equal to the Radeon HD 6670 DDR5 graphics card or just slightly better. The Radeon HD 7750 is basically equal to the Radoen HD 5770 / HD 6770 (same card, different name).