I have ubuntu 6.06 on my old comp for rossetta@home number crunching. I have tried opensuse (awesome), dsl and others. I plan on moving my parents comp to ubuntu :D, and buying a system76 laptop.
You can put any graphics card in it as long as it has the right connector (probably pci express in your case). You'll probably have to install the drivers for it though.Remember to turn the machine off and unplug the power cord and ground yourself when you go in the case and all that jazz. There...