makes excellent sticks. You did not say what kind of playing you do. I use the 5-A myself and I steer clear of the heavier woods such as Oak, which I find as being too heavy. The last time I used a "B" stick was when I was in marching band, where heavy hitting is a must.
I am not familiar with the "extreme" series of sticks. Perhaps you could check out the Firth website and see whether those sticks are still being made and if so, where you can purchase them, and what the differences are between the various sticks.