Pioneer x2700Bs, x4700bs are my two personal favorites. These units have network mode with 3 way crossovers to setup the Sq system you want and it 13 band eqs with time alignment which is a must for any Sq setup. Rear cam, front cam on the x4700, USB, Bluetooth all built in.
Consider running no rear speakers because it will pull the stage back and ruin the detail due to cancellation if not done properly. It also wouldn't make any sense if you want just pure Sq as possible.
Tweeters are a must with Sq. You will need to play with positions to see if you like them on axis, off axis, on the A pillar, sail panel, etc... My two favorite spots are a pillars and sail panels because theyre easy to access and most of the time one or the two provide the sound im looking for while retaining a level of stock look.
Personally id recommend Hybrid Audio Imagine components, Focal Access, Morel Tempo, Hertz HSK isnt bad, DD CS6.5, DD BC6.5 and theres a German set that is equivalent to 2 sets of the Cs, that I recommend highly.
Sub wise you need tight accurare bass to blend with the front stage. There are Sq marketed subs but they are not so easy to come by in Trinidad so that one you will need to decide out of whats available. I personally chose the DD 500 8" series and crossed over at 63hz at -12db via an old model pioneer double din unit, it works nicely with tons of head room even though im feeding it a solid 550w rms.
You will need a nice class a/B amp to run your mids and highs and if doing just fronts alone for pure front stage you may need a 4 channel to run the tweeters and woofers active to have total control over them to get the best sound.
Bass wise youll be able to decide when you choose the sub. I think infinity / jbl are the same and very Sq oriented subs able to handle a bit of power.
Hope that helps, I've done a few front staged systems with no rear speakers and the results have been great. I don't have the money even at budget level to run active processing yet but even so the results aren't bad with passive crossovers.