proycraft - the main problem you will have will be that the fish you plan to introduce together are already mostly adult. This will lead to fights.
I have a 125 with a jag, JD ,3 GT, salvini, 2 firemouths , rhambidia(?) cat and 3 plecos. I recently removed a pair of jags outof it and an eel (24"). These fish do not really fight - mainly because they have been together since 1.5" and the tank has a lot of structure.
If you introduce your fish into a 125 - 150 , make sure you set up plenty of hidingspots, claypots and fake plants. That will help in keeping down the aggression. Next, as scott mentions , you need to preform big waterchanges - weekly. Many people keeping CA cichlids do 50% weekly.
IME jags are opportunistic feeders and not really aggressive unless the tank is way too small, barren , dirty or they are breeding.
JD you are right about, I have found them quite docile however my biggest is only 7".
Cons as any breeding cichlids will be terratorial and aggressive. If you can provide enough structure and hidingspots you should be allright.
Jewels can be nasty - when breeding. It's been a while since I had them but I don't remember them being particularly mean on a daily basis.
Oscars are big and messy - this fish will contribute considerable waste. Some people love them but I would go without. Another problem with them is that they seem to be very prone to diseases due to the messy conditions they create and once they become scarred I think they get plain ugly.
Blackbelt have a nasty reputation - though I have never had them.
Pikes - haven't had any but at the same size as the others I think they do OK as they are fast and have big mouths. If they fall behind in size thy become food.
Remember that nothing is written in stone , so get the tank you can afford and are comfortable with and just monitor the fish closley - especially in the beginning and be prepared to remove some and bring them back to the store.
One last thing, fish are individual and will have individual personallities which means what is impossibly aggressive for someone may be docile for you. If you set things up reasonably your chances for success will increase.