I've just swapped over to the 4 ohm taps on the Primaluna EVO 400 Integrated playing through my Klipsch Forte III's.
I'm stunned!
More body in the sound. Bass more rich and defined. Totally solid sound at high listening volumes.
Late night low volume listening is also absolutely awesome. It's like hitting the Loudness button in the 'good ole days' but with equal mids and highs mixed with beefy bass!
I'm shocked! But oh so happy!