The Dell XPS 15s are deluxe laptops that look great. This is true for both models we tested, but we definitely prefer the version with Core i7 and GT 640M over the one with Core i5 and GT 630M. The i7 version costs more of course, but it's worth the extra money. The processor is quite a bit faster, and you can actually play games with that graphics card.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips