Take a look at a Homefill II unit here:
http://www.invacare.com/cgi-bin/imhq...odID=IOH200PC4
and then take a look at the EX2000:
http://www.dichroicimagery.com/produ...ducts_id=18136
You'll see that the shape of the compressor unit is exactly the same and the oxygen outlet is in the same place. Basically, I think the EX2000 is probably a painted Homefill compressor (and perhaps a few stickers) with a few minor modifications to allow attachement to a cga540 and any oxycon.
I am not sure why anyone would buy an EX2000...it is just too expensive at close to $4000. Especially when used Homefill compressors can be had for $450-650. Add $200-300 more for fittings and doodads, and add your own oxycon and tank, and a tank-filling system on par with the ex2000 can be had for less than $1k instead of $4k, for a savings of $3K.
$3k in savings buys a brand spanking new GTT Lynx, Phantom, or Mirage, plus a whole lot of color. Hell, $3k is a healthy mortgage payment or two...