The TDK Indi DVD 840G and the Plextor PX-708A are essentially just rebranded versions of the same unit - and both have recieved pretty solid reviews. They can also write 4x DVD+Rs at 8x. Nice.
In fact all 3 of the units you mention are reviewed and compared in one article:
http://reviews-zdnet.com.com/TDK_Ind...tml?tag=subnav Even better.
Remember that all of these are INTERNAL drives. The HP DVD Movie Writer dc4000? Never heard of it! However, you're paying a premium of $100 for it being external and the analogue capture.