Here's a great step-by-step on figuring this out. I suspect it's either one of the new adds or the amp/stereo. But it could just be a short. There is also the off chance it could be a dead cell in the battery, so you should consider having that tested, as well.
How to Find and Stop Car Battery Drains ? DIY Car Battery Drain
How to Find and Stop Car Battery Drains ? DIY Car Battery Drain