You need to be very SPECIFIC in your question.
1. Does cost include Windows OS, monitors and other peripherals?
2. Please verify COUNTRY.
3. Is this for playing video games primarily?
Also..
$650 is not a high-end build. Anyway, depending on the above answers something like an i3-6100 or similar might be your best start and the best GPU the budget can fit in whilst choosing relatively good quality for motherboard, PSU etc.
*The main difference the extra $150 gets you is perhaps a slightly better CPU and Graphics Card.
use pcpartpicker as a guide