ok, to clear up some fallacies. Eps 4, 5, and 6 are _not_ available only on "low-quality vhs". They were released (numerous times) on Laserdisc (which is near-dvd quality). Also, in spite of the fact that they will play in your dvd player, VCDs are nowhere near the quality of DVDs. Depending on who encoded them, they sit either just worse or just better than VHS. SuperVCDs get closer to DVD, but the resolution is still much lower and the audio is still only stereo.
BTW, there was never a licensed release of any Star Wars on DVD. It is most likely a pirated rip of the laserdisc or, more likely, the vcd version.