As I am in the business, let me impart what knowledge I have concerning CD/DVD duplication controllers and towers.
There are thre major CD/DVD duplicator manufacturers.
Wytron: They are based in Taipei, have been around for awhile and their products are considered well built, speed and compatibility are good. There top of the line model is the DVD-688, works well with major brands of writers. They have a compatibility list on their web page. 64 mb of buffer memory, which I believe is plenty.
ACard: Again, based in Taipei. They feature a lot of IDE/SCSI/RAID adapter cards as well as their duplicator products. The build quality is a little cheap looking but the speed seems good. ACard sells a lot to OEMs, so you might see their product being rebranded. Be carefull though, on the ACard manufacturer website, they advertise their controllers as having up to 64 mb of buffer memory, but you will see a lot of OEMs advertising the same product with 128 mb of buffer. This is done by tweaking the firmware to show "128 mb" on the LCD. I do not know if ACard has any new models that really do have 128mb buffer though.
An Chen/CopyStar: Another Taipei manufacturer. They sell a lot through OEM channels so you might see their products under a lot of other names. Build quality looks a little cheap but speeds seem good. Again, beware of the 128mb buffer claims. I have seen An Chen boards with dummy memory chips and re-labeled memory chips to make them look like 128mb. Some OEMs are really sneaky this way.
VINPOWERDIGITAL/ILY: These two big OEMS seem to have found a mainland China manufacturer that makes boards for them. I have one of these boards in front of me for demo purposes. Build quality looks a little cheap but the board runs OK. Speed is good. The board has only one 64mb buffer chip but the LCD reports 128 buffer though.
Summary. I have my own preferences, Wytron, but what people really want is copies, not duplicators. If you want to buy a duplicator tower, try to find one that has enough power. 400 watts or above for a 10 target tower. Aluminum cases are nice but other things are more important. Leave the side off a regular tower if you need extra cooling. You could just buy the controller and a case of drives and just stack them on either side of the controller,(you would need to scrounge a couple of old PC power supplies though)
As far as media is concerned, you can go first class and buy Tayo Uden or some other top quality media, or you can do what the pirates do and buy the cheapest media you can get and just accept the 10% to 20% reject rate.
Finally, if you want good quality and speed, try to integrate a hard drive into the unit, it really helps.