I've always had good luck on Linux with Nvidia cards. My older desktop has an Nvidia 6800 in it that works great, and my new laptop has an Nvidia GeForce Go 7700 in it.

If you're having lockup issues with your system and Nvidia cards, you might want to consider upgrading your power supply. Nvidia cards do consume a lot of power, and your typical Dell with on-board video on the motherboard, and an el-cheapo power supply just barely adequate for running that motherboard, might not be able to deliver all the amps the Nvidia card needs.