The DVD drive in the Liteon systems should be able to handle good quality 4x or 8x rated media. This meadia is also slightly cheaper than 16x media.
I would suggest either real TY or Verbatim media. am yet to test my 5055GDL+ with some 16x media.
I think the drive inside the unit is limited to 2.4x or 4x burning though as a copy from HDD to DVD is not exatly quick BUT it is alot quicker than direct recording.