Best place to buy steel in islamabad

First of all,i want to know if anybody has the information about current steel rates.
Secondly,if someone with experiance shed some light on various things that should be kept in mind before buying steel for construction.
What are the pro and cons of using 60 vs 40 grade steel in a resdential double story house.
Why is islamabad steel so talked about and considered relieable compared to gujranwala or lahore made steel even if construction is not going to take place in or near islamabad.