Has anyone installed a subwoofer? I just want to add a little more punch to the system without drowning out the rest of the speakers or rattling everything. Right now I'm looking at Xtant A series subs and a X3.1 amp. I'm trying to decide between one 12" or 2 10". If someone who has installed a sub could give the specs on their system and if they think its enough/not enough, I'd appreciate it. Thanks.