One of the problems with sub's and Quads is the speed issue. Quads are very fast and clean. Dynamic subs, no so much, unless you have small cone drivers properly implemented and even then the frequencies handled by the cross over slopes will lose some clarity. So if you are at all fussy about sound quality, and I assume you are for chosing Quads in the first place, I would not go there. I tried it and never go it close to right.
But all is not lost! First lots of folks put the Quads on stands. This can put a hole in the upper bass and make them sound thin in the upper bass/midrange. The were originally designed to be on the floor! And, with very careful positioning, on the floor you can get relatively flat FR to 35hz. And, once you have heard good electrostatic (or planer) bass you will have a hard time listening to dynamic woofers. :-)
I went back to dynamic speakers some years ago, but not because of any issues I had with the bass part of the FR.
If you must have loud sub 60hz bass, be sure to get a high quality cross over which has a steep slope roll off of the sub's FR above 60 hz and run the Quads full range.
Good luck.
But all is not lost! First lots of folks put the Quads on stands. This can put a hole in the upper bass and make them sound thin in the upper bass/midrange. The were originally designed to be on the floor! And, with very careful positioning, on the floor you can get relatively flat FR to 35hz. And, once you have heard good electrostatic (or planer) bass you will have a hard time listening to dynamic woofers. :-)
I went back to dynamic speakers some years ago, but not because of any issues I had with the bass part of the FR.
If you must have loud sub 60hz bass, be sure to get a high quality cross over which has a steep slope roll off of the sub's FR above 60 hz and run the Quads full range.
Good luck.