[SR-Users] Request of advice about TAS for IMS

I am trying to setup a really simple (I hope so) IMS platform, with some basic services (like voicemail, IVR, videoconference), but I'm kind of stuck. I have installed Kamailio IMS on debian and a OpenIMS VM also. But my little problem begins when I try to configure a application server (in this case, a TAS). I have tried with Elastix 3.0 (kamailio+asterisk), asterisk alone, and read some about Restcomm. For Elastix and asterisk, I get stuck trying to setup the trigger point. For Restcomm, I only find documentation for integration with Clearwater IMS. So, I need your help. Somebody has something like that working? What TAS (or components for a TAS) do you recommend? Tutorials, examples, manuals that you know can help me? Thanks for reading, and many many thanks for any advice. David