i am thibking to buy a new pc at budget of 35k so i have a problem my prblem is i am buying intel i5 3570k with intel hd 4000 igpu . the igpu is not good so my question is if i put any other gpu in my mobo they will work together just like i put any old gpu with dx 10 supported then i put it in my mobo the power of dx 11 of intel hd 4000 and the performance of any old gpu will work together to make a great fps rate
Thats around 600-650 USD for the PC and ~$70 for the GPU
You won't be able to get your integrated GPU to work with a discrete card, the discrete card will be significantly more powerful anyway so the IGP wouldn't help much even if it could. If you put a GPU in your motherboard that is only DX 10 capable it will only be DX 10 capable because it is the primary output, the IGP in the CPU cannot help it or add bonus features.
You should be able to get something around a 6670 with that budget, the performance won't be spectacular at high resolutions when gaming but it will be alright and significantly better than the Intel HD 4000, it will handle basic tasks like web browsing and movie viewing with ease.
7770 is a decent step up from the 6670/7750 (7750 is the new name for 6670)
mostly it will game ok at 1080 resolution or less.
*when you insert a GPU the iGPU turns itself off. Only AMD has the possibility of using the iGPU and the GPU at the same time for more graphics power (and only with AMD GPU's). This is known as Hybrid Crossfire.