postgresql to support 50GB of data?

We are building a distributed application where we need to support the
database of around 50GB in size. Also there will be around 300 users
connected to the system. The database server needs to be up 24/7.

Please suggest whether postgresql is capable to handle this kind of
load and data? Also please suggest what kind of hardware (number
of processors, RAM, etc.) will be needed to get a good speed of
execution from the database?

sorry for some vague parameters like speed and number of requests
per sec.

thanks,

hitesh