Elk + Homeseer + Sonos?


I am planning on installing an Elk-M1G, and have Sonos throughout the house.  I would like to be able to play my own recorded announcements (like you would do with an Elk-124) in various areas of the house, but would like to use the Sonos speakers that are already in the various zones to output the audio rather than Elk speakers. I would also like to have the 2-way communication offered by the Elk-TWA/TWI.
Has anyone successfully achieved this?  Perhaps by adding Homeseer as the mediator between the two systems and placing Elk-M1TWM microphones in strategic locations?
If so, do I still need an Elk-124?  An Elk-TWI?
Perhaps Homeseer offers all of this (including self-recorded announcements) without the Elk cards?
Any guidance would be most helpful. Thanks!
If your goal is simply to play announcements based on ELK activity, then you can do that with HS, the ELK M1G plugin and the Sonos plugin - I do it all day.  ELK activity can trigger a HS event that can do pretty much anything you want.  HS can output text-to-speech so it can say anything you want, as well as mp3 and wav files, or combinations.   If you use some simple scripts, the speech and sounds can be customized even more based on conditions you specify.  For example, my arrive-home messages are customized based on who disarmed the alarm.   Sonos can play the messages to whatever speakers you specify, so the limit is your imagination.
The ELK-124 becomes irrelevant because HS can do so much more.
I do not have a two-way, so I don't know what I'm missing there.  But there is no reason you can't use that independent of HS.  HS also has speech recognition if you really want to talk to your ELK.  :)
Thank you so much for the reply!  The Homeseer website is hard to extract useful information from... do you know if I can do all of that you mentioned with the HS4-Pi version of the software running on a Raspberry Pi, or would I need to go up to the Standard or Pro versions running on a PC?  I'm hoping for the Pi option. Thanks!
I don't know about the Raspberry Pi version - I suggest you go over to the HS forums and ask about compatibility of the ELK and Sonos plugins with the Pi version of HS4.