[NAME] Rohlman  Do you have an XPS 8940 or XPS 8950? I think you'd get better and more predictable cooling enhancements by upgrading the case fan(s), rather than messing with thermal paste, which may -or not- help. And you'd have to redo the paste every so often, when it dries out, while a fan should be a more permanent enhancement. The XPS 8950 was designed with a bigger case and more attention to cooling which clearly were issues on the XPS 8940. So that should help. IMO, use things as is and see what temps are like with summertime heat. Then decide what to do, if anything... Assuming you have an XPS 8950, check to see if you have the Intel Innovation Platform Framework  driver installed, which "...supports Intel Dynamic Tuning Technology (Intel DTT) and Intel Context Sensing Technology (Intel CST). Intel Dynamic Tuning is a power and thermal management solution that is used to resolve fan noise, overheating, and performance-related issues of the system..." You could also install something like Speccy (free) to monitor temps. You can configure it to launch at boot and put its icon on the taskbar which shows one temp (eg, CPU) all the time. Mousing over it shows a popup with the other temps it's monitoring (eg, GPU, HDD, SSD). IIRC, a user posted that SpeedFan (free) can adjust fan speeds in the XPS 8950, something it couldn't do on most older Dell PCs. So you might want to give that a try too...
Has anyone swapped to noctua fans and or replaced the thermal paste on their CPU (aio water cooled) or on their GPU?  Curious if there were any performance gains from using like thermal grizzly or anything.
XPS 8940/8950, fan/thermal paste