What is the new system intended for please? Different purposes would require different components.
If the system is intended for producing large amounts of DVD copies, then there are only two realistic alternatives available:
1. Purchase a duplicating machine.
2. Contract a duplicating service to do the job for you.
If you intend to produce large quantities of different DVDs then you could add another controller card and more drives, as thespy has suggested, but as Alex mentioned earlier you'll most likely end up with lots of 'bad burns' anyway. I'm also unaware of any software designed for burning multiple DVDs concurrently or in unattended 'batch' fashion.