Branded PCs are much expensive than the hardware configuration they provide.
If you are willing to buy a PC go for a assembled one because you can set what you want in your PC. Nothing is limited , you can assemble as much hardware you want within your budget.
Here are some tips to choose correct hardware parts:
1. Set your budget ( for example. 25-30k)
2. Put out your needs.
Like RAM, Hard Disk, Graphics card, Optical drives, CPU, Cabinet, motherboard, PSU.
3. 4-8GB RAM is recommended for optimum processing.
4. You can choose i3, i5 or a faster and cheaper AMD chips.
5. Choose a perfect cabinet that should not be larger or smaller than required.
6. Get a supported motherboard for the system to be installed.
7. 500GB-2TB Hard disks are recommended.
8. Choose a powerful PSU to power your system.
9. If you are planning for a gaming PC get a Nvidia graphics card.
10. A 1280* 720 HD monitor is recommended.
And peripherals according to your choice.
Hope you got some information