Happy upcoming 30th! $300 will buy you a very nice brush.
Some questions to allow folks to give you some suggestions:
What kind of brushes do you like?
What do you currently own?
If you are looking for large brush - Shavemac makes some extremely large brushes. I am a huge Simpsons fan. They make some pretty hefty brushes as well, Chubby 3, Tulip 4 and Polo 12, for example.