$1200 is a nice budget for a solid car audio system. It's strange though you start design by.. looking at bass speakers.. I'd say that part is the easiest to get right.
However, this budget is still kind of tight for a complete SQ system. I would say, to save some cash go with a single quality 5-channel amplifier. Get something very solid. My personal favorites on tight budget are:
Alpine MRX-V60
Kenwood XR-5S
Precision Power "Power Class"
I prefer to use amplifiers that have excellent results based on third party measurements (and not just the wattage, but other specs as well, like THD, channel separation, efficiency, etc), and these had performed excellent on the benches.
A five channel amplifier can be used in a variety of ways. 2-way active front stage+subwoofer. Front+rear+subwoofer. Bridged for front+subwoofer, etc.
In terms of front speakers, get something nice at once instead of looking for "the great $100 bargain" only to replace it later. Some nice 2-way speakers to run in passive mode are Focal Polyglass 165 V30 and Hybrid Audio Unity. It's often possible to find Focals locally at around $400 and the HAT's cost $350 online. If you would like to play with active fronts, I could recommend Hybrid Audio Imagine. They are basically like Unity, but with a primitive passive crossover (and it doesn't matter, since they will be run active, but they're much cheaper than Unity). I have had great success with these HAT Imagines running active off an MB Quart amplifier (with a 2.2uF capacitor inline for the tweeters). Running active means that I can level match the volume of the tweeters and woofers, and also use time alignment on tweeters and woofers separately from each other. The results are pretty good.
Stereo: My personal preference is to have a stereo with these three things: bluetooth, time alignment, rear usb port.
Sub stage: With a 5-channel amplifier, you're usually limited to having 250-350watts of power running to subwoofers, so you need to choose a subwoofer accordingly. I would have picked two 10 inch Dayton Audio HF subwoofers (the 4ohm version), wire them in parallel, and run then in a 1.5cu ft sealed box. These are among the best SQ drivers that also have very good sensitivity. I also would not hesitate to run a single 12 inch Image Dynamic IDQv3 or Infinity Kappa 120.9w on this kind of power.
Midbass: IMO.. skip the dedicated midbass driver. Start with nice 2-way speakers in front, and a good subwoofer. Decide later if you need a dedicated midbass. I run HAT Imagine 2-way speakers in my car and a 12 inch subwoofer, and I really do fell like I have more midbass now than I really need.
Wiring kit: StreetWires 4awg kit should be enough (the one that comes with 150amp fuse, not the 100amp one). Price is around $60-$80 online.
