Home stereo channel,energy no the same loudness, power?

So like 4 years agol, I got hooked into getting speakers and bang in my room, my room estereo wasnt good, if I try connecting more speakers the less power each would get. So I moved to a house and happen to find a stereo no speakers, philips magnavox, 1999, so its max volume went up to 40, but no way I would turn it up to 40 cuz it will blow all my 10 speakers around my room, I would bearly turn it up to 15 volumesl, and hily S*** it be so loud. Now if 20 then speakers would most likely burn. So yah the stereo was very strong. Time past and idk what I did to it. Now I have gotten a stereo on craigslist, philips magnavox. The same one I had found, and reason I got it was bcuz I thought it do the samething as the otherone. But it didnt. So im wondering hiw is it possible? Their the same so is their sonlmething I can do to make it like the other stereo? I opened it cuz I thought you could change the something since it said voltage selection 120v 120v- or 220v 220v- but maybe thats not it. Well if soneone can help and explain ill give 10 points. Thanks...sorry for grammar, using phone