buy laptop with minimum hardware or a fully loaded one?

It depends on the company you are looking to buy from. Some companies (like Alienware) are known for charging an arm and a leg for the smallest of upgrades. Check out killernotebooks.com, they offer reasonable prices for upgrades. For the most part though, upgrading on your own may be cheaper. Easiest way to find out: Go to the site of the company you are looking at. See how much they want to upgrade a specific part and then go to newegg.com and compare the price.