Radeon cards generally run at a lower temperature than GeForce cards, and their "Ultimate" versions are actually designed with passive cooling. This can be a good choice if you want to build a silent computer or just don't want to rely on mortal fan bearings. Purchasing a card from a good manufacturer would also work of course. You should expect any decent video card to have protection against an eventual fan failure, and the best ones will have thermal sensors too. Thermal sensors, by the way, are integrated into the new Radeon XTs I heard, and future Catalyst drivers are supposed to take advantage of them with automatic throttle control (i.e. overclock when cool, software rendering when hot). New hardware like this isn't going to come cheap of course. If budget is any concern to you, I would stick with a Radeon 9600 Pro, either from a good manufacturer with proper fail safes, or go with the Ultimate version at a small premium.
Something to keep in mind with D2 is that it was designed to work with Glide, so an old Vodoo card will actually outperform any Radeon or GeForce you can purchase today. Before you persue a video card upgrade, consider switching the game to DirectDraw mode instead of Direct3D. This should improve your D2 performance significantly without any drawback. All that lag around Diablo's pentagram, A2 Tyrael, or A3 rivers will be gone in a snap. You can even survive Shenk's fireworks if you have enough system RAM. There's also the option of using Foxbat's D2 Accelerator to reduce some graphical effects and help slower systems cope with the game.
Something to keep in mind with D2 is that it was designed to work with Glide, so an old Vodoo card will actually outperform any Radeon or GeForce you can purchase today. Before you persue a video card upgrade, consider switching the game to DirectDraw mode instead of Direct3D. This should improve your D2 performance significantly without any drawback. All that lag around Diablo's pentagram, A2 Tyrael, or A3 rivers will be gone in a snap. You can even survive Shenk's fireworks if you have enough system RAM. There's also the option of using Foxbat's D2 Accelerator to reduce some graphical effects and help slower systems cope with the game.