The 2500 series is the best SQ you're gunna get from DD. It's all downhill from there lol. Output is a different story...1.8cf tuned to 37.5hz with 36sq" of port made my 2510 come to life and sounded decent so I could only imagine what a 3500 could have done. I know some are gonna cry foul but the DD did have a kinda hollow sound to it though not saying it sounded bad but it did have a much different sound then other subs I have used. But on the other hand the eclipse is a beast in its on right and is nothing to look down at.
DD because I could care less about sq