I have a Hafler DH-500 amplifier powering 2 RTA-12B speakers and I am consistently blowing the 3/4 amp fuses that protect the tweeters when I play at high volume but less than 12:00 (1/2 power) set at the preamp (Hafler DH-110).
Other threads have suggested the Hafler is underpowered for the speakers playing at high volumes, but my understanding is the DH-500 is one of the more powerful vintage amplifiers out there. The RTA-12Bs are rated to handle 500 watts.
My Hafler was was checked out by a Hafler knowledgeable technician and he said it met or exceeded all specs (255 watts/channel into 8 ohms).
I would welcome any suggestions/opinions.