Where's your RJ31X? Is it in the Telephone Distribution panel, or do you not have one? Just in case you're not familiar with what an RJ31X is, it's a special telephone jack for the alarm panel that goes in front of all the house phones - as the very first thing off the phone line; that way if the Alarm needs the phone line, it can seize the line no matter what's going on - outbound call, off-hook phone, incoming call, etc... So it wouldn't be a chain like you listed above - there's a loop off the main line to the M1 then back to the rest of the house phones.
**** I just read up on the Elk 950 - it's not just a surge, it's an RJ31X too, but I'm leaving the above for others....
OK - so with that said, the Elk 950 needs to go in front of the distribution panel - so, the following:
DEMARC > Surge Suppressor > DSL Filter > Elk 950 Surge {to Elk M1 and back} > Telephone Distribution Panel
Note: I'm not sure how many people understand the DSL filters at the DMARC end, but if you're going to have DSL in your home, IMO it's the only way to go - using one splits the incoming line from the phone company out before ever going to all the jacks in the house, kinda like just having two phone lines - and keeps you from needing those irritating filters on every single phone... so much better! And if doing anything like running your phones through a gate control/intercom or into a phone system, it's about the only *right* way to do it that won't cause you to lose internet every time the intercom is used.