You were probably confused by the Panasonic marketing claims which are not based on the physical speed of the drive.
The E80 only supports 1x dubbing to DVD-R (2x to DVD-RAM). A 1x high speed dub of a 2 hour SP recording will take about an hour to dub to DVD-R and 30 minutes to dub to DVD-RAM. So you only need to buy 1x disks. Although the 2x and 4x will still work.
The E100 does dub at 4x to DVD-R.