I owned a pair of MDA-300 monoblocks in the late 80's, early 90's. They generated a lot of heat, but I loved the sound. My wife convinced me to sell them because of the heat and high power bills. Selling these (and my Cello Audio Palette) are my biggest regrets in my audiophile journey.
I bought an FPB-300 in the late 90's and owned it until one channel started distorting last year. Given it's age, I decided to sell it as-is instead of getting it repaired. This was another great sounding amp, although I think I liked the MDA-300 better (different system, different room, so direct comparisons aren't possible).
The obvious issue with these older amps is that they will need service at some point (more likely sooner than later) and some of the parts are no longer available so re-engineering can get expensive.
I bought an FPB-300 in the late 90's and owned it until one channel started distorting last year. Given it's age, I decided to sell it as-is instead of getting it repaired. This was another great sounding amp, although I think I liked the MDA-300 better (different system, different room, so direct comparisons aren't possible).
The obvious issue with these older amps is that they will need service at some point (more likely sooner than later) and some of the parts are no longer available so re-engineering can get expensive.