config file question between versions 7.4 - 9.1

in the config file for 7.4 we have an entry:

shared_buffers = 1000 # min 16, at least max_connections*2, 8KB each

in 9.1 the default is:

shared_buffers = 32MB 

max connections is the default 100

Do I need to make any adjustments or can I leave it at the default?

The machine is dedicated to Postgres and has 8GB of memory and a default install of 9.1 and 7.4 doesn't appear to have any custom configuration.

Thanks!

Randy