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 ;)