Burning more than one dvd at a time

This seems simple, but I think that there maybe more to it.

I want burn 4 dvds at a time. As of now, I have two DVD burners installed in my system. An 8x Lite on and a 4x sony. I am using RecordNow DX, which allows me to select both drives. When I do a test write using BeALL 4x disc, I receive an error towards the end of the process.

Is the because I am using two different models?

I want to burn more, up to burning 4 at a time. Can I install a PCI IDE card and add two more drives? Can I use the one available IDE slot on a PCI card already installed? Will RecordNOw DX ‘see’ the drives on the pci card?

I could use any and all suggestions, please. I have to burn 2 sets of discs- 50 in each set.

Thanks!!

oh yea, I am using an AMD 2400 on an ASUS mobo, with 1gig ram. 3 WDs 8mb HDs (200GB - 120GB - 80GB) and two firewire (180GB-120GB). I already have on PCI card running my 200GB drive. I have a pci card for 3 added firewire, plus firewire built into the mobo. APG 8x gainward with 128MB, dual display. Incase any of that matters.

Plus, if I need all the same burners, what should I use?