Any advice on what an optimum networking solution would be appreciated. We need to upgrade our server and wanted some expert advice on what our system should like.

We are a design manufacturing company that relies heavily on our computer usage for design as well as interfacing with shop equipment. Server related issues can be enormously expensive
Current:

15 workstations
set up for remote access (3-5 users)
server 2003
switch
router
linked photocopier/printers 2
Symantec anti-virus
Tape Backup
NAS backup
DSL connection

Thinking:

Primary server (new) for file/printer handling
Second servery (old) for remote access and redundancy if primary server fails
NAS - mirrored and interlaced
Symantec, or is there something better?
Eliminate tape backup and replace with another NAS or portable hard drive? WD Passport?
Cisco Firewall? or other better?

Are we missing anything or should we be doing something different?

What is the best way to eliminate IM and restrict internet access?

Any advice would be greatly appreciated.

Thank you in advance.