I ran the 8 watt ASL AQ1005dt with 90dB ACI sapphires and it did fine except with orchestral and bass heavy rock. It really shined with Omega TS2's (94dB) and I could play it as loud as I thought practical with just about any music.
Here's an excellent illustration of just how critical synergy is with SET, and that it's not just a numbers game: In contrast to your results with the ACI Saphhires, just yesterday I plugged my Quicksilver 300B SET's into my Soliloquy 5.3's which are a wonderful floorstanding speaker with some authorative bass response that, like the Sapphires, are also rated at 90db sensitivity. My SET amps put out 8 watts at 8 ohms, similar to your AQ's. My experience of my own pairing off was that the SET amps in this case were really not able to handle any bass demands, and when the music got really complex, dynamic and or layered it sounded absolutely horrible. This is a shocking thing to hear coming from what is a fabulous pair of SET amps. Mind you there were some things it could play magnificently, creating a remarkable sense of atmosphere and presence, but those would be offset by other recordings the combo simply could not keep pace with. Now if I'd just purchased those amps, and matched them up with those speakers because the numbers made some sense, I would be setting myself up for some MAJOR dissapointment (I'm not suggesting that you implied this Entrope - just trying to share some experience here). Put those same SET amps with my LaScalas (104db) and they are absolutely wonderful! Those same Soliloquy 5.3's were an outstanding match for my 11 watt push/pull mono 10's, which really isn't that much additional power at all! But it's not SET, it's Push/Pull. The ACI Sapphires you mention are a 2-way monitor speaker. The Sol's are have three drivers to push and have a much larger cabinet with rear porting. Consequently they are moving a lot more air, or rather enough to make it just difficult enough for the SET to fall out of the realms of consideration for these speakers.
Again, the lesson here is do take care in speaker matching, and whenever possible audition with a wide variety of music. It is well worth the investment of your time and care as the righ combination is quite stunning. Another directoin you may want to consider offering similar strengths of SET in some ways with it's own unique spin, are OTL amps. Again, matching those up with the right speakers is critical as well, though perhaps not quite as demanding as the lower powered SET amps.
Marco