Content management solution w/ linux server?

Hello, I am looking for a CMS that uses a linux server for indexing. It 
will be utilized within a medical setting so strong, flexible ACLs are a 
must. Also file conversion tools (to allow us to use handhelds to view 
word docs and such as HTML) would be good. We do not want to spend more 
then 10 grand for 25 concurrent users. The users will be on windows WSs, 
the only reason the server should be linux is support considerations. A 
fully managed appliance is fine as long as the damn thing does not run 
windows. Any help would be greatly appreciated.

--Eric Moore