Hello! I was planning to get the JBL NSP1 II system with the PB10 or PB12 subs, but have then read several reviews about users having AMP issues with these subs (stop working) plus humming noises when left in stand-by mode. Is there a real quality issue with these units? If so, what sub woofer can I get to work with these speakers at a similar price point ($200 - $300 sub)? I will be using this system in my living room (20 x 20) with a Denon 2803. Thanks!