Need advice about 300mm 2.8 (I'm a lucky dog)

[Francis]

Yesterday I turned 5.
And my mommy and daddy gave me a card that said:  300mm F2.8

I just about exploded! I've taken tens of thousands of bird photos over 
the last few years, all with a good but not quite well suited K200mm 2.5.

So now the question is which one should I get? Have any of you used one 
of the old Tamron 300mm f2.8? Are they A enabled or is it green button 
material? And when they say "for canon FD" or for something else, does 
that just mean it has that adapter on it? Or are they mount specific? 
how about the older Tokina telephotos? Are they good (and cheapish)?

Any suggestions on this would be muchly appreciated!

Yours truly,
Francis

(a Canadian)