Sonic frontiers sfs 80 or 160

I dont know what the impedance curve is on the Quest-Z, but if it is anything like the the Aerius, I would not recommend it. The SFS-80 uses very little negative feedback. While this really makes for a pure sound, it also creates a high output impedance, which means that coupling it with a very low impedance electrostat speaker will cause somewhat large fluctuations in frequency response. With the aerius, you would lose a lot of treble with one of these amps. (-5db at 15khz)

I have the SFS-80 and have used it in a couple of speakers.

See this article: http://www.stereophile.com/reference/810/index.html

On the other hand, with other speakers, these amps sound fantastic.

Franczyk makes an interesting point with some merit. I've never matched my SFS or SFM amps up to a Quest Z. However most tube amps do have a higher output impedence than a tube amp and its not unusual to find them going as high as 3.5 for the SFS80 (as I recall this was the impedence measured years ago by Stereophile). I have used the SFS 80 with Acoustats, Quads, and Paragon Jubilee/Jems and have never noted a highend roll off noted by Franczyk.

The SFM is notibly more powerful in the bass and more neutral in the mid range than the SFS. These are very smooth amps which are detailed and only a tad toward the warm side. I have used them with the Quads, the J/J's and Tyler Linbrook Systems successfully.

I listened to the Power 2's - very dynamic and resolving. A tad cool for my tastes, but an excellent amp. I'm not sure I'd consider the ML line a good match unless your sonic preferences are on the very cool side of neutral.

Hope that helps you a bit.

I have the Quest Z and am happy with using my ARC VT-60
as long as it is biwired and you use all the 4 ohm tap of the ARC VT-60 your fine,but if you try driving them any other way they simply run out of gas and won't pump out hardly any bass at all.

I have owned the SFS-80 and very comfortably driven the Martin Logan SL3's... Actually that combo had magic that I have found hard to reproduce until throwing MUCH more money at the components. I have also heard the SL3's driven by the SFM-160's which was even better. I am not certain how they would do on the Quest Z, however I would opt for the SFM-160's if you can. I personally would avoid the Power 2 and Power 3 as the sonics changed quite a bit from a very musical amp to a much cooler amp, more neutral and less emotional/involving. Good luck.