The Dell XPS 15, as it is sold new by Dell, is no longer worth buying because the 1920x1080 display upgrade is no longer offered.
15.6" 1366x768 displays, such as the stock display offered with the Dell XPS 15 and now the only display option it offers, make things onscreen large and tend to have very poor image quality due to low contrast. I recommend against buying laptops that have this type of display to those who have a budget that allows them to get a laptop that has a better display and still suits their needs, and who don't require larger text for eyesight-related reasons.
If you don't mind a refurbished laptop, however, you can still find a refurbished Dell XPS 15 that offers the upgraded 1920x1080 B+RGLED display. Follow this link to the Dell Outlet section for the Dell XPS 15, and look for one that lists 15.6 inch FHD (1080p) B+RGLED Display with 2.0 MP webcam under "Click here for available options and upgrades" and under the specific specifications for the model you choose. Avoid the models that do not list this.
However, an alternative laptop that has great speakers and a great display is the Sony Vaio F.