Elastix 1.6 and above will install fine on the Dell T100 server but I do not recommend that type of server if you want a good quality voice server, I have tested a few of these servers with Rhino interface cards and when using PCIE (express) type of boards the server freeze if you send a few concurrent of calls trough the PCIE server. I think the problems is that the T100 just share to much interrupt with other internal devices and there is no way in the current Bios to have the PCIE slot on its own interrupts.
I did not test the T110 but its in the same price range and most of the time you get what you pay for. If you really want a reliable server I would advice to buy a Rhino server with a rhino card. They cost a lithe more but they also works good. I did not test the elastix servers yet so I can not tell you how good they are.