[DIGIUM?] *Compatible* list of Brand servers for TDM cards?

After purchasing Dell SC420’s and 750 Rack servers we later saw months later the notes about incompatibility with the Digium TDM cards (to our expense and disappointment - as like many we use Dell servers exclusively for years).

*** The relevant question we would love to have answered is what Brand name servers are known to work?

Being a Dell server only business, we are now in a difficult and anooying situation that the TDM cards are just low-budget enough not to be compatible with the server grade equipment of one of the top 2 manufacturers in the world.

Anyone, preferrably Digium?