Looking for suggestions for backup system

I am looking for some suggestions for solid, reliable and RESTORABLE backup system.

Here is my basic configuration that I want/need to backup:

Two Windows 2003 servers:

ServerA: MS-SQL running a 3rd party accounting software and also is the Active Directory.  Total backup requirement today is about 20GB's.

ServerB: MS-Exchange and also is an AD server.  Total backup requirement today is about 35GB's

My basic requirements for a backup system are are follows:
1) Full and complete backup of both the systems without shutting down the server processes
2) Would prefer a single-tape solution, but if no tape can handle total data load, then tape juke box and use of multiple tapes is fine.
3) Would prefer NOT to use NTBackup, (unless someone can convince me that it is 100% reliable on restores)
4) Need to be able to backup and restore ONLY the Active Directory from the Windows Server environment without having to backup the entire System State of the servers.
5) Would prefer capability to be able to backup and restore individual mailboxes in Exchange.
6) Pretty much has to be a Windows Server solution, (I.e. not a Linux/Unix solution)
7) Be able to administer the tape system from an administrative workstation instead of from the server only

For now, those are my basic requirements.  
Given that, what hardware and software configurations, (and some ballpark costs), would anyone suggest I look to?

Thank you,