but the id8s only use half the wattage rms of the rockford or kicker. i realize double the wattage is only what 3db gain, but what is 5mm of xmax, more than 3db?If you want sound quality and output. I would do either the jl audio w3v3's or the image dynamics ID3'S. Both can be had for around 120 a piece. Sound quality is excellent on both models. But the ID3's have more output which make them louder. The ID3's have more surface area and xmax than the W3's. ID3's have 15mm of xmax and W3's only have 10mm of xmax. 10mm is about standard for 8 inch subs. 15mm is excellent for 8 inch subs. You look at rockford and kicker 8 sub specs all around 9 and 10 xmax. Just average subs.