I can see why the Pioneer would cause problems with those speakers. At very high output when the receiver is hitting it's operating ceiling it's clipping power nearly matches the RMS handling on the T55s, and PSB is even as specific to say 125 RMS less than 10% of the time. This means if you were clipping this would be the tipping point for the poor tweeters on those speakers. I've previously owned PSB speakers and I can say without a doubt in my mind, they require clean power to sound their best and to be kept safe from damage. I noted on more than one occasion when using the PSBs I had that combined with how hard they where to drive, and my desire for high output that a mere receiver wouldn't do, and I thought my tweeters were damaged because of the horrible sounds they made. I got a Carver AV-505 power amplifier and suddenly realized it wasn't the tweeters, it was the Onkyo TX-DS787 receiver I had been using to drive
them, which is slightly larger than your Pioneer VSX-1018. The AV-505 had a tremendous amount of headroom and an ability to drive virtually any speaker.
My PSBs were a bit of an odd case because they were a small floor speaker, but they were around 85dB 1w/1m and 4 ohms making them incredibly hard to drive to the levels I wanted (I was young and wanted it freaken loud). After getting the AV-505 I realized they could take just about anything the AV-505 had to offer as well, and those PSBs are some of the loudest small speakers I've ever heard, it has to be heard to believe. They were also some of the least delicate of speakers I've owned, but damn did they crank something fierce.