Just came across this this morning, now that Steam officially supports Ubuntu, should be useful.
http://www.howtogeek.com/132549/6-tips-for-improving-game-performance-with-steam-on-linux/ (http://www.howtogeek.com/132549/6-tips-for-improving-game-performance-with-steam-on-linux/)
Good find I will have to read it manage some success in this but more help the better