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 ;)
A well chosen amp certainly can tame your highs. As you have already found, your Kappa's are going to be hard to beat. If you like them, then shop amps instead.
An amp upgrade could certainly tame your top end peakiness. I've had some issues with metal domes tweeters in the past trying to balance detail with harshness. The Wyred4Sound ST-500 has a soft top end, gobs of power with good bottom end slam and control, is detailed, and images well. There are many reviews available for more details. I found it a pleasant amp, dynamic when necessary and yet capable of subtleties as well. It would probably partner up well with the Kappas.

Another option would be cables/plugs to tame the high end (though I would loose the Yamaha regardless). Good luck.
Thanks. The PSB's sound great, don't get me wrong, but $3500-5500 better?? It would take an in-home trial to really compare, of course, but then again, if that's the only way to tell, then that's too close to be worth that much $$.

Ok, so we have a vote for the ST500....any other experienced ears able to offer suggestions?