Loopmasters.com
^They have a sample pack for almost anything you need genre wise. Don't be afraid to use samples, it's all about creativity. And ADSR doesnt really translate to percussive sounds unless you are making kick drums from scratch from a synthesizer; if that's the case then it is extremely difficult to make hard hitting commercial sounding kick drums. My advice is to find some bomb ass samples and go from there. Be sure to use a glue compressor on any drums you might be layering.