Grenadier Guards project.

So i have started a new strategy for this army this time.I am collecting everything i pretty much needed first.Before i paint them and assemble the Infantry.So here is what i got and few piks. 
what i have. 
9 open fire shermans 
3 fireflies open fire 
1 set of regular bf Sherans with firefly, was going to use theese as commmand models 
5 Bf 1/2 traxs 
5 point of contact 1/2 tracks 

Infantry 
alot of Bren gunner teams for the 1/2 tracks , 2 Infantry platoons 
medium mortar team 
heavy mortar team 
vickers mg team 
Engineers 

So here s what i need still. 
Trucks,for the Infantry 
Artillery 

Universal carriers 

So here is my dilema on what to get next . 
Arty,it is toss up 5.5 or 25 pounders? 
Stuarts or Cromwells? 
Armored cars? 
extra firefly? 
For the Stuarts or cromwells question. i just probably buy both.How does the BF compare to psc? i heard that the PSC stuarts are a bit large.how is the PSC cromwells? 
As for List i will be playing Armored Grenadier Guards LW. 
As for choice what you prefer to have?or buy all of them eventually.But which ones should get next?i would like to at least be able to field them here in the near future after we finish up are d day caMPign games and Start Market Garden.Especially with Blood Bowl Season starting up here soon.Then mext year we start on are weird war(SCI-Fi ,Goth Horror,ww2 1945-? ) 15mm games.NAzis ,Aliens and Zombies what fun! Hitler should not have made a deal with the Aliens for UFo tech.Now they turned on him and deciede to take over the planet for themselves.