I asked my car battery would drain with these parties and whether it would be a good thing to get all this for $ 300. It was not a box or if any wires. I have 4 son class already so it does not really matter.

This is not a 2000w amp. With brands like that, you need to look beyond what is printed on the box because the brands at low prices Always hide the number of RMS power and generally swell anyway.
It has 2x40A fuses if you're looking at 800-1000W. This should not stress, at least not too much, most actions charging systems. I do not mess with the CAP personally. They do not help the weak charging system and do nothing advantageous in general.
I'm running 1500W RMS with a 110A alternator and battery actions.
I have a small headlight dimming, but all things considered it works very well.

But this amp and 2 12L7 is worth $ 300 especially if it is in good shape.

Edit: In response to the comment of Odin "-" And the radios do not drain car batteries, unless you play with the engine off! "
While the powers of the alternator's electrical system in the car while the engine is running - it is important to recognize that once the alternator output has been exceeded is the battery that takes relay. Thus, it is certainly possible that a high power is more power from the alternator to a point that it can weaken the battery, even with the car running.