The A21 has got a good dose of current to back up its power. As long as it’s used within its limits then I’ve found the amp ample power. On the other hand if constant disco like listening like are the goal then perhaps alternative amplification or speakers should probably be considered.WOW a week power bill must be through the roof
Granted the amp can handle more than people think and newer versions can handle more with the larger power supplies but this is preface lift
I've lived with the a21sig day in day out for the last 2 years for 6-8hr most evenings (and the OP even longer with his 2004 model I'm sure) watching tv, listening to music and podcasts and my experience tells me otherwise.
It would be a poor combo unless used for background music , I'm sure it sounds nice, fantastic in fact at lower volumes as my Revels did, but when the tracks get demanding or loud the amp will lose steam very quickly with speakers like that, 4ohm and 85-87db (which is probably optimistic) in fact these MA's are more demanding than my Revels where. I suspect the MA's drop to 3ohms in some places and stay there for quite a while with bass-heavy tracks ( most dealers don't listen to bass-heavy tracks that I'm referring to here) the little Sugden certainly wouldn't like that at a higher volume.
I could certainly see it in the cone movement swinging wildly indicating the amp has lost control and that wasn't even at 1 quarter on the volume dial, this was 7, 8 o'clock on the dial. Above that, you then start getting the strange weak bass as the amp runs out of puff again my experience with "demanding" speakers.
Some are using Kef ls50's and reporting good things but judging how hard they are to run with a "normal" AB amp i find that hard to believe as well but some are after different things.
Something about the speaker has to be easy eg 10ohm 87db (proarc tablette 10s) or 6-8ohm 90- 99db (Klipsch heresy 3 or Sugdens own line of speakers) there is nothing efficient or sensitive about the MA 100s. Fine speakers for sure but id certainly be staying away from this combo. The a21 SE id think a little different.
As I've said I'm sure it sounds lovely and sweet at lower everyday levels but if the OP has any Inclination at all to turn it up at all then id think twice.
I do also listen to content which is bass heavy and like previously said the performance of the A21 in combination with a NDX 2, 5G Gold 100 and a Fathom f112 v2 is simply sublime.
Btw, if you haven’t already done so then I would look at brining into play a subwoofer or two. If the sub/s are aligned, calibrated and dialled in effectively then the system should sound better overall then the same electronics and main loudspeakers used without a sub/s at higher playback levels.
Imo, a subwoofer is the most important main component.