The most efficient way to go about this process is as follows. First, make a list of what components you need. Once you know the specs of your ideal computer, go to a general review site to help you make a decision about the best brand. You will for example, be able to find a Inspiron 5160 review there.
Next, go to the brand site and use the comparison tables to find the model that most closely matches your specs. Finally, run a search for that specific model, such as the Inspiron 5160. This will bring up many sites and allow you to find your best price. Then you are free to make your purchasing decision and well informed to boot.