Hi, I am new to subs. I am currently connecting the subs to the amp speaker output and the speakers are then connected thru the sub per owners manila.. My amp do not have a sub output but has a preamp output. Can I use the amp's preamp output for the sub?? Another question, what is the minimum amp power required to drive this sub. Its a power sub, whats the different with the speaker? I cannot find the info in owners manual. I have a small Đ amp which has only 18W/ch can I use it to drive this sub??