From our very limited experience with using one PS400 with Opi's 250s at one point during the second Mid-Atlantic get-together, I'd have to agree. I can't explain why the Crowns sound so good at my house with so many different JBLs over so many decades, but they sounded thin and, yeah, maybe "edgy" and "bright" when hooked up to Opi's system in which he uses three Perreaux amps. We didn't spend a lot of time checking pre-amp settings, etc, and as I recall our routing to integrate the amp may have run it through the Sony HT preamp in use but controlled it with one of my Soundcraftsmen Pro-Control pre-amps, too. Regardless, even if there were pre-existing EQ setting or pre-amp coloration involved, the Crown was not as pleasing on the 250s as the in-house system was, so we didn't listen for very long.
My family can attest to the bi-amp Crowns being anything but "edgy" or "bright" in our house with our 4345s. And I've have no such complaint with any of my seven Crown amps with any of my over-a-dozen JBLs, from 4345s to 030s, but the experience with Opi's system is why I suggested you investigate the Perreaux amps in the first place for your 250tis. :dont-know