I don't disagree w/ you about subs having a place of their own in any system, it is just in my case, and perhaps others, the 4's actually suffer from having a stand alone sub as opposed to bi-amping the 'subs' that are built in to the nht 4's. Using the two a1's (200/250/300w @ 8/6/4 ohms respectively ea. mono amp)to drive each 10in driver in the 4's will gives greater control, slam, and is completely adjustable by the x2 controls which has continuos adjustable phase, boundary compensation, and lfe level to tune rather than placing sub in 'ideal' spot. There is no doubt that a powered sub would be needed for the 3's to get the best of a&v. Besides, a 'good' sub would cost more than my mains and many people don't consider a really good sub costing more than the mains/monitors.