I'm not familiar with Peachtree, but that amp is Class D. In reading some of the previous posts, room treatments are good, but I think that high frequencies are less affected by room. That's why tweeters are usually recommended to be at ear level, they are not as robust as other frequencies. But other frequencies can certainly be an issue.
And sibilance, or a distortion like sound coming from the tweeters, is probably not room gain related. Is there a possibility that your Yamaha receiver is straining at higher levels?
And sibilance, or a distortion like sound coming from the tweeters, is probably not room gain related. Is there a possibility that your Yamaha receiver is straining at higher levels?