Speaking of which, the core would be 5 players IF Chabot, Tkachuk, Norris, Stutzle & Sanderson are identified as the core players. Hypothetically, if all five are given max term, $8 m contracts, that's $40 m right there.
Although I haven't done a detailed analysis, I'd guess there haven't been many successful teams that paid more than that for their core. Tampa has just recently reached (or exceeded) this situation. But, if someone wants to do additional research, by all means, that input would be welcome.
If you add Debrincat at $8 m, that's a 6 player core and $48 m of cap. That assumes that future contracts don't creep up and exceed the $8 m/yr.
Most teams have to make adjustments (subtractions) when they approach or get to that point. So, I'll guess that the Senators will need to do this at some point. It seems inevitable.