The Dell XPS line is terrible....
http://www.hardocp.com/article.html?art=OTI0
read the reviews and you'll see for a "Gaming system" it comes preloaded with useless garbage to take up system resources, plus they do not come with restore discs which you should be entitled to. They come preinstalled on a hidden partition on the hard drive and most dells do not give you the option to create the disc. Wheh the HD fails and you replace it you have to call up dell for the restore discs and their support is definitely one of the worst I've seen.
As far as the dell laptops that are overheating... most of them use a regular Desktop Pentium 4 with hyperthreading. While they are fast and moderately priced they generate the same amount of heat as a desktop processor, and it spells trouble for most laptops because they provide inadequate cooling. They usually work fine but many are equipped with thin finned heatsinks that clog very easily with dust.
The same goes for Toshiba's... the S209 series seem to be the most troublesome as most of them use desktop pentium 4 cpu's. Working for an authorized repair center, usually we see the most toshiba's coming in.
I'm a big fan of the asus barebones. They are pricier but you can pretty much pick your components.
Sorry to sound so negative... I'm just not a fan of laptops as much of a desktop person. I fix both desktops, laptops and IPODs and parts are usually more expensive than desktop components and can sometimes be harder to find. I usually find myself resoldering components instead of replacing things just to avoid the hassle and the extensive costs.