I own 3 400m for left right center. I’ve had them out in the open on amp stands and I’ve had all three in my audio video cabinet. For an amp not class D pumping this much watts and current they just do not get beyond warm ever. My room is not big. I’ve had them for a very long time. Never an issue. Never a hiccup in quality. They are not much to drool over looks wise but as stated I had them in my cabinet. Not that they are ugly either just not a Luxman but built like a tank. The sound is pretty outstanding but it is a mono version of the 330a. Expect more up the ladder.
I’ve auditioned the 860a and it was awesome. To me deeper into the details. Better stage. Maybe a touch sweeter. But quite a bit more money. I usually stuck with 400m at dealer when auditioning speakers as is what I owned.
As stated shoot for the moon is pretty awesome. You can climb to next levels in the line first year and get a full credit from your purchase towards an upgrade or in year 2, lose 25%. It really is pretty great if you want to enjoy the first year or two while saving additional funds to move up.
I think you would be thrilled with the 400m. The size, the weight, the sound are pretty great in this range. 10 year warranty, top rate customer service. And barely warm is the word of the day.
Older review about sums it up.
https://www.soundstagehifi.com/index.php/equipment-reviews/231-simaudio-moon-400m-mono-amplifiers