I know this post is old but for posterities sake I’ll leave a comment:
I have the Luxman 505uxii (class A/B) on my Forte IV’s. Sounds amazing. Super clean and controlled. The sound is large and lifelike. I’ve tried low power tube amps from Decware as well as higher powered tube amps from AR (vintage) and the 505 blows them all away.
In my experience the Fortes perform much, much better with higher powered amps. Especially with amps that can control the bass. The 505 has tone controls that work very well, as well.