I know that I'm just repeating myself but we really need to go in another direction. The M777 is a good gun for what it was designed for and we have enough of them. We need something SPish.
The K9 thunder purchase was for 38 guns and spare parts for 134 million Euro which is CA$185 today. That's reasonable and would be enough to outfit two regiments complete, which together with the M777s would properly outfit the CA as it is currently configured.
I'm partial to K9 if for no other reason that it is in mass production which is also why I like the M109/1299 series. When it comes to wheels I'd wait out the US program for its Stryker brigades because whatever they choose will likely create a large enough number to ensure parts stability for some time. Archer is just too few as it is and even Caesar with 76 sold to Saudi Arabia is barely touching on 200 as it stands.
The US has 8 SBCTs - equipping them alone would add 144 units plus training and tech spares to the inventory of whatever gets bought together with a robust maintenance line. I must admit one thing though. With the move to the US Force 2030 divisional structures where an SBCT shows up in the Heavy Div alongside two ABCTs, it wouldn't surprise me at all if the div's arty bde will standardize on an M109 across the board. I'm not sure how many Heavy divisions they are going to end up with but the structure doesn't seem to account for all 8 SBCTs.