Gaffar market in Karol Bagh is another best option to buy electronic stuff.
It will be preferable to buy laptops offline near Nehru Place or at any other showroom of Dell or whatever you wanna purchase
You can buy them on amazon as well. It will offer great discounts too
Laxmi nagar would be the best place
You can try amazon... But u should prefer nehru place there's wide variety available there.