What about a $25 "quickie" reader drive?
It's very popular for on-the-fly purposes.
Of course, fastest on-the fly copy times are acheived by:
Reader drive on motherboard's primary master IDE channel, alone on the cable
Writer drive on motherboard's secondary master IDE channel, alone on the cable
Hard drives on SCSI, SATA, or an add-in IDE card.
Motherboard's bios (standard section) set to auto detect and auto type the primary master and secondary master, as this will give the best chance for full performance of your optical drives. You may choose primary slave and secondary slave set to "none" to prevent the motherboard from hunting for devices that do not exist and save time during startup.
In all cases, use high quality, modern, medium-short length interconnect cables that are not cramped or touching other cables in computer case. There is only one brand of round cable that fully conforms to UDMA specs, but most 80 wire ribbon cables perform well. A powerful, low noise, name brand power supply is also necessary. With these, it is possible to put drives onto seperate power channels to eliminate the power issues that cause additional PIFs.
Have a great deal of RAM installed in the computer system to prevent the idiotic, and very slow, trick/issue of Microsoft Windows using the hard drive memory swap file to contain the writing software's buffer. Reducing the writing software's buffer to fit in available free memory is vital to on-the fly duplication. So, have as much free memory as possible/budget allows.
With these issues addressed, you should have full 16x speeds.
Basically, it's having each device on its own controller that will give you the speed you need.