Someone with more knowledge can correct me but AFAIK dry powder extinguishers are on the way out now, because they can incapacitate someone in a small space eg in cabin of a vehicle. In fact, Motorsport UK now bans it for in-vehicle extinguishers, you have to have AFFF foam or ZERO2000 instead, 1.75kg minimum.
If you already have a powder extinguisher I would probably keep it as it'll be better than not having one and you can still use it from outside (eg on an engine fire), but if buying a new one better to go for AFFF I think. You'll find it hard to make room for a 1.75 or 2kg bottle so will probably need to compromise to something a bit smaller for the Cali.
Please can someone with expertise check this though.