wow, this thread started yesterday and you guys are already harassing me because i havent responded? 
The ones i purchased from DDM tuning are 55w ballasts, with hi/lo beams, and ultra small/slim ballasts (probably 2"x2.5")
i've been extremely happy with their products as well as service. I had one of my bulbs pop because i touched it with my finger... called them, and they sent me a new one for $16 plus shipping.
Their bulbs were very accurate and bright on my VX, great cut off line with minimal glare.
i personally took my whole front end apart to install mine because i wanted it to all look factory when you looked under the hood. So i hid a lot of the kit behind the bumper like eric (etlsport) said.
I can explain the difference in cost to you, because my cousin actually lives 4or 5 blocks from ddm tuning. He runs an LS6 sand buggy with probably 10-12 headlights on it, all HID from DDM.
DDM tuning has a HUGE warehouse FULL of kits. My cousin tells me that their warehouse is the size of a home depot, full of HID kits. Basically, they are the wal mart of HIDs, so they can afford to sell them for less and repair/service them for little to nothing.
i would recommend them to all my VX friends and fam.
"Do Not Seek Praise. Seek Criticism."
"If You Can't Solve A Problem, It's Because You're Playing By The Rules."
"The Perosn Who Doesn't Make Mistakes Is Unlikely To Make Anything."
-Paul Arden