to burners is a waste. I once experminted with dual 4x SCSI drives back in the day. At the time, Nero was pretty new, but had dual burner support. Kinda neat burning two copies of a disc at once, but how many copies of something do you really need?
I currently do all my stuff with a single optical drive. It's a BTC 8x burner. If I rip a DVD, it rips to the hard drive, then I shrink it, then I burn it to a new disc. Same for audio and anything else.
Also, can you even get 16x media? 8x is hard enough to find as it is. I burn at 4x on my memorex media.