I will not bore you with the different types of sound amplifiers available out there, the main point is that your next purchase should be a new amplifier that is a class D model also equipped with a switching power supply. If you can afford it.
Improved Circuit Protection
Besides the efficiency and weight of the class D amplifier another important consideration is to find out how the amplifier will react to a shorted cable or when connected to the wrong speaker impedance. This will in causing the amplifier to fail if not protected from the bad connection. The newer amps will simply mute the audio, protecting its circuit until the error is fixed. They return back on-line automatically bring the speakers back up.
I have experienced amps that will shutdown the bad circuit but will not return to back on even after you fix the problem. I would be required to turn off the amplifier, count a few seconds then turn it back on again before the downed speakers came back up. This was a stereo amp with only one side shutting down due to a bad cable.
In still another amplifier, both channels went out and the fuse I needed to replace was in the amplifier requiring me to open the chassis completely to replace the fuse. I simply purchased a new fuse mount and relocated the fuse on the outside of the amplifier (Mackie 808s).
Class D Amplifiers are Best for Church Outreaches
I recently purchased two of these newer amplifiers for with my church outreach and commercial gigs. Each of these amps drew only about 350 watts of power at maximum output and only weighed 7 lbs. Using amplifiers with low power requirements make a lot of sense when using generator power out in a park.
Are the Old School Amplifiers Any Good?
These models that may draw 1000 watts of power each and weight nearly 50 lbs each. They will work well but be sure to test all used equipment before purchasing them.
When it comes to Electronic Equipment, How old is Too Old?
Okay here are the real scoops about dealing with old electronic equipment and this holds true for sound, video, communications, and other electronic equipment. How long will the electronics last? You may be surprised to learn that I have used equipment that was nearing 15 years old. Actually electronics as old as 20 years will work too its just that I don’t want to be mistaken for an antique dealer when showing up to do sound (drum tap and a 
cymbal crash). Except for electrolytic capacitors (the round cylinder shaped components with a + one side and a – on the other), everything else electronic will last longer than you think.