I just installed a DEQX Pre 8 in a system based on Magico S7 loudspeakers. First off, they are extraordinarily well made. To start, they were being driven by McIntosh gear. The image was diffuse and details smoothed over in typical McIntosh fashion. There were two JL Audio Fathom subs using a low pass filter only and the bass was confused. The room is a dedicated media room 20 X 30 feet with a 9 foot ceiling. After replacing the mac preamp with the DEQX the image snapped into focus and details were audible that were glossed over before. Adjusting the treble down a bit gave a neutral sound without any sibilance. The bass now managed by the DEQX was eons better but still lacking in the utmost definition, the fault lies with the Fathoms. We are going to replace the Mac amps with a pair of Bricasti Design M28s and I am sure that will bring this system up into the upper echelons of performance with the exception of the bass below 50 Hz. We have not discussed new subs yet, I would like to see four Martin Logan BF 212s.
In short, The S7s are a fine speaker and a reasonable value given that you can spend a lot more for the same performance. As you see here they can be no better than the equipment in front of them. This is true of any great loudspeaker.