Hakumei, you are using linux as "for life" system?

What games can be played on 'NIX? WoW, old Quake 3, Nexuiz, OpenTTD, what other good? I think that Linux is mostly for server system, not for workstation...
Also, did the low core speed of AMD processor affects on game speed in old games, which not use multiple cores? (Yours Core Speed is about 1400 MHz, is that enough)? Does exist more speedy cores AMD?
I asks because I thought about upgrade, and watch AMD side...