I am new to car audio and need some help with what i would need for a subs as powerful as the BTL's. I heard you need a charging system for your amp to keep up with it, but im not sure what that is. Also what kind of amp would i need for, lets say 2 15" BTL's

Okay well what people mean by a charging system is that if you get an amp that puts the BTL to it's full potential (2000 watts) you are going to need to provide that amp with more electricity than your stock car can produce. This is acheived with a High output alternator and extra battery(s). High output alternators are vehicle and engine specific. Companies like Iraggi and DC are some i can reccommend. Batteries: lots of people suggest XS power. A kinetic hc2400 is always a good choice too. 2 BTL's is a lot of power. I would get a high output alt and 2 big ol' batteries at least. as for an amp... that really depends on your budget. If you have the cash, Sundown SAZ-4500.

Thanks a lot, I appreciate it i'm starting to understand a lot more

No problem man! Not sure how much research you've done so i apologize if i seem to be insulting your intelligence; but a BTL setup or any setup up in that wattage range is not cheap. At all. The price of the woofer(s) is only about 1/4 of the price of the install. FYI, i spent 2k on my BTL setup and its a single 18. I could have easily spent more and i plan on it in the future when i have the funds. Bumping a'int cheap!

Good luck with your build!!!