the 4000 and 4000R look EXACTLY like those, for $300 and $350 respectively. I know because I got my 4000R last week.
http://www.vitalityweb.com/backstore/ems4000.htm
and whatever the specs are, that sucker can push me farther than I can stand it, so no worries on it being inadequate, at least for a lightweight like me.
John