I would recommend you picking up a pair of the MBRP long tube headers, MBRP or Bassani X pipe, high flow cats (SLP makes nice stainless pieces for cheap), and to finish it off the Magnaflow Magnapacks sound really nice. I'd run 3" front to rear, The Boss 302 intake is going to set you back roughly $500 but will give you a lot of grunt in the upper RPM band and I would match that with L&M airflows 82MM throttle body which is going for about $400. JLT makes beautiful pieces as far as the cold air set ups go so i would hit them up for that. You're going to need to pick up a flash tuner or PEMU, I would highly recommend you going to Anderson Ford Motorsports and picking up their PMS system, it is by far the best Programmer in the game and will allow you to tune everything you put into the car from larger injectors all the way up to the nastiest twin turbo supercharged or nitrous injected set up you could imagine. The PMS will cost you about a grand but is well worth it in the long run. Also the Boss 302 intake sits a little higher than the stock one so you may have clearance issues with your strut brace.
I don't know what kind of impedence those subs are or what your amp is rated at in regards to RMS and such but you're probably going to need to look into at least a 2Farad cap and depending on how big of a load your amp is going to pull on your electrical system i'm not sure if your alternator is a 130AMP, but if you're going to push more than 800RMS through your system you may run into issues.
Pretty much a capacitor is a reservoir of energy capable of releasing large amounts of current very quickly when your system requires a lot of bass. But picture the capacitor in the system like this, you have the power coming from your electrical system and it's represented as a skinny hose, and your cap is a bucket capable of holding a lot of energy and it has a large hose coming out of it. Now if your electrical system cannot keep up with the energy that capacitor is discharging it's going to pull that energy from your battery/alternator.
So going off your stock specs on your alternator at a modest 64% efficiency your stock electrical system can handle roughly 1164.8Watts RMS MAX, keep in mind you're sharing this number with the load that the rest of your cars electrical system puts on it. So I don't think you're going to be able to handle a 1500WRMS load on your system at this point. Personally you really don't need that much, that is just outright insane inside a stang. I would dial down your amp to 800WRMS and just roll with that, trust me that is going to shake the crap out of everything inside your interior. I'm only running 2 P2D4's with a P1000X4D amp and I'm only using half the amps RMS rating and it will rattle the interior all day.