It’s my opinion (which is worth nothing) that the house sound comes with McIntosh amps that have Autoformers. I’ve had non autoformer MAC amps (MC7106 and MC7100) that, while super clean, just didn’t have the house sound. All 4 of my autoformer amps I have now have that intangible house sound. The 7100 series amps are no longer around...
I spent quite a bit of time behind an MC754 back when those amps were fairly new and never really warmed up to that amp...and maybe that was due to it not being an Autoformer design.