"According to Philips it will not be possible to upgrade existing 8x DVD recorders to DL layer recorders, contrary to what some rumours are saying. In theory the laser power of an 8x drive is strong enough to handle DL but the problem is, is that the OPU (Optical Pickup Unit) of the drive is often not good enough. This will lead to quality problems. However, some drives with good OPUs could, in theory, be upgraded although theyâ€™d have to be handpicked."
"More interesting is that they will also introduce the ND-2510A drive supporting dual layer DVD+R recording. The ND-2510A drive will basically be the same drive as the ND-2500A but with a different firmware. Before any of you start thinking about upgrading the ND-2500A into a ND-2510A, just upgrading the firmware is not enough. Just as Philips said, the drive has to have a higher quality OPU for it to handle DL properly. The ND-2510A is expected to be released in May."