I have currently Reference Audio 4 channel amp with No Sub. I have planned to upgrade to Pioneer 6500F amp and really dont know about the sub. My range is around 4-5k for a sub. My pre is 3550ui Pioneer and I have no clue on how will I run my sub without mono amp (I am not gonna buy that). Please suggest me a sub as I will be putting it in a sealed box as I dont need earth shaking bass. I need decent bass (SQ quality) so suggest me box too for a sub i.e dimensions etc. And also tell me if Pioneer 6500F is any good in that range because shopkeeper always misguide you to sell their crappy products first.