I'm an IT Consultant. We will analyze what exactly is it that you need, compare the technical specifications, see best sites for prices, options for guaranty and after selling services.
Local shops are also included, because after selling services are important and returning policy (if it's broken within the first year, you can get it replaced, not repaired. Or money back if it can't be repaired). There all kind of cases and it's best to analyze the options in your country.