that's a question that only you can answer. But ask yourself: how much do you need them; or can you rely on what you already got?
That being said the m12 tools that I have used (drill & hacksaw) have been great.
Ryobi 18v chain saw $30.03
I don't know if it's any good, and I would bet that it isn't for heavy cutting, but Home Depot has their Ryobi 10" 18v chain saw with a lithium battery & charger on clearance for $30.03