Hi, I was wondering if anyone could tell me what the difference is between a cl D amp and a cl BD amp?

I am thinking of getting an amp and some subs for my car and i heard that alpine amps are the best so im thinking of getting 2 1500w alpine type r sups and then hooking up some kind of amp to it but im not sure which one will do the best job. I listen to mostly rap and i just want something thats going to give me the best b. The few amps i looked at are either type d or type bd so im not sure which one is better or which one i would want. The amps im looking at are 1000w so does that mean that i'll need 2 amps to give me something close to the 1500w for the subs or will i be fine with just one 1000w amp. thanks