I came across some interesting artifacts and real life test results on a comparison between the latest ball bearing Turbo by Garret and a classic Journal bearing Turbo and the results are suprising,so therefore you might want to think twice before you go out and trash a couple of grand on a Garret Turbo upgrade for your Mazdaspeed3.
http://forum.e46fanatics.com/showthread.php?t=588344
http://forum.e46fanatics.com/showthread.php?t=588344