Terminal server with 50 users simultanious

Hi!

We have 50 users and are considering a Windows 2003 server running as
a terminal server. All of the users are going to work at the terminal
server instead of locally.

They are going to use an SQL client where the SQL server is placed on
a different server than the terminal server. They are also going to
work with e-mail, office programs including excel, word, access and
powerpoint along with other applications that they normally run at
their local computer. All of the data for these applications is placed
on the DC.

Do we need 2 terminal servers or is one powerful one enough? How many
CPU's is appopriate? Should we go for 64bit OS and CPU's so RAM isn't
an issue?

I'll be very greatful for any feedback to this post!

Regards
Oystein Sund