I am in a similar search for a pre amp for the S5.5 for my 99db Forte 3’s and from just doing paper research on preamp, am leaning towards Backert Labs Rhumba Extreme 1.4 or Rhythm 1.4 balanced line stage. Would have to part with my 1yr old perfect CSiB, new mint Technics 1210GR TT in box, Mac C27 pre, ARC SP8 pre and Mac MC2125 amp first for the economics to work out but seriously considering doing that.
On the S5.5, its WPC rating is 50wpc @ 8 ohms class A. 100wpc @ 4 ohms AB. 100 amps. My concern is if Magnepans can be comfortably driven with the S5.5 (86 db, 4 ohm, require high current) without stressing the amp. Any input on how the S5.5 handles Maggies or electrostats is of definite interest! Thanks.