can a new amp amp tame my speakers?


Just spent some time listening to what I've been planning to upgrade to for main speakers. PSB Synchronys. The Imagine T2's are close, but slightly veiled in comparison. My current, but old, Infinity Kappa 7's really don't give much away to the PSB's. My amp is an old Yamaha MX2, 125wpc, and I've heard them described as bright or harsh, and that's the only complaint I really have with the sound now. Can a well-chosen amp tame the highs on the Kappa'a, which use a ribbon-style tweeter? Or is the 'taming' I seek only going to happen with a speaker upgrade. I honestly don't mind upgrading the speakers, and fully expected to, but after today's auditioning, I'm wondering if I'm going to get that much benefit from that level of investment. $3500+ is a healthy chunk of coin for benefits of slimmer profile and tamed highs. In terms of imaging, weight, and bass, the Kappa's are equal, imo. The system is also the theater, but the avr can power the surrounds, so an amp upgrade could be 2 channel. A power boost is a must too, as the current 125wpc isn't enough for when wifey's not home and the volume gets wound up ;)
english210
can anyone offer opinions of a Peachtree 220 amp as an option for taming the highs on my speakers?
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I'm surprised no one asked what kind of preamp is being used. That could easily be the problem.
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Possibly, but it's a Yamaha AVR, hardly audiophile quality, but since the issue is only an issue at higher volumes, it seems to be a power amp issue - a new pre isn't in the cards for now, the room is also the family/tv/movie room.
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?
My thought is the amp is straining, hence the thread. The receiver is running an outboard MX2 amp, 125wpc (although somewhere I read it was 150). Perhaps there's a gain issue between the avr and amp, but as both are Yamaha, I didn't really consider that. All I can say is that movies/tv are usually around -15 to -20db on the volume display. When I'm really cranking it, 2 channel, home alone, etc, I'll crank it up to 0db or possibly higher. the 'max' is +16.5. Does that mean anything to anyone in absolute terms? I understood it better when volume controls were a simple 1-10...
Anyway, since the problem is only a problem for me at 'I have the house to myself, time to let the neighbors know I'm home' volumes, I'm reasonably sure it's the amp running out of power.