Well like you said 650 meg CDR was around and then 700 megs pop up..After that 800 meg generics and such arised..
But DVD9 is Pressed from what I heard with half and half of Audio and Video..For the time being there is NO DUAL LAYER Burner on the market..NOT ANYTIME SOON. Since technology is advancing it will happen just don't know when..
Closest thing is DVD-Ram drive which has 9.4 media's..
Go to
www.doom9.net
This is dedicated forum for DVD issues..
For now A04 is the Best..My case A03 with Ext Firewire which does Fastest maximum Stable Output..It's Great..