Crown use to publish in their owners manuals charts for appropriate fuses for a given power level for a given impedance. They also had drawings of early protection circuits you could build. We installed discos all over Mexico and the Southwest of the US, and I never lost a driver using Crowns recommendations and circuits. When Mcintosh developed amps with Power Guard we were able to increase the amount of power per driver when bi-amping or tri-amping without driver failure from 50 to 100% over just fuses alone, or using unprotected amps with peak limiters or RMS compression. But you have to understand the specifications of the speaker. If it is pre digital in design the peak to average signal handling capacity of a speaker was normally 6 db. Meaning your speakers could handle 200 watts published specs. But only 50 watts continuous. Now music is not continuous noise, but does have peaks. When disco came along synthesizers became very prominent in the recording industry. They can generate a lot of high frequency content not found with acoustical instruments, forcing manufacturers of speakers to increase the HF capabilities of their speakers. When CD's arrived in 83, with their increased peak capability and larger Dynamic range, speakers had to be further strengthened. So with that all in mind your speakers are fairly efficient at 94 db at 2.8 volts which is a bit over 1 watt with your 6 ohm impedance. So I doubt you'll be using more than 20 watts for the midrange and 50 watts for the bass if your an average listener for peaks.
I would have looked for a pre-owned Mcintosh Power Amp with Power Guard which prevents clipping, and restricts the power of the amp to about 25% over rated power and to less than 2% distortion for peaks. So, a 2125, 2155, or 7150 would have been my choices. To save money a 754, 2120, 2150 or a 7100 with out the meters. Now as long as the Power guard is only activated for short periods, fractions of a second , a few times hourly your speakers will be very safe. You won't hear any distortion and your speakers will be protected. Drive the amp to where the Power Guard lamps flash more than 20 % of the time your speakers may not totally fail but will suffer. I Have seen B&O, braun, ADS speakers destroyed in a flash being over driven by Crown, Yamaha, Marantz and Mcintosh amps with out protection of Power Guard circuits. So be careful. And remember its better have to much power you will never use than to have to little with the possibility of high distortion reaching your speakers and causing the drivers to fail.
Crown also use to publish their versions of Murphys Law. You know what will not go wrong will sort of thing. And one of their Laws was to the effect output transistors blow first to protect speaker fuses. So tread with caution. At the first instance you think you hear the slight change in upper frequency characteristics turn the volume down and let the voice coils cool. I would recommend at least an hour.
