Certainly it's better a stereo amplifier, but the choice is mine and I'd rather do it as simple as possible!
And for the power supply, it's just a power supply that I had at home and I thought that maybe I could use it. But in fact it's not suitable.
I tried to do it this way: Final class A stage, 2 common source stages in the middle and a differential amplifier as the first stage. All with a feedback. But I can't make it work with PSpice, perhaps because how i'm doing it, is very complicated!!!