I can understand how you would believe those things, but sorry, guys, you are both wrong. I speak from hard won experience.
alex0203, you CAN use a SS guitar amp to play an acoustic/electric, but you will be unhappy with the results. Even a clean channel or clean electric guitar amp is built to sound (more or less) like vintage tube amps played clean, which unintentionally colored the sound. Most A/E guitars have an under-saddle pizeo pickup in them, and they sound horrible just amplified- nothing like an
acoustic guitar played through a microphone. Acoustic guitar amps often have DSP circuitry that makes the A/E guitar sound more acoustic-like- chorus, reverb optimized for acoustic guitar, etc. Also sometimes feedback-killer circuitry, etc. This is also part of why you can't expect optimal a/e guitar amplification from a PA system.
If you have an high-end piezo pickup WITH a acoustic-optimized pre-amp, you can do just fine with a PA.
Some bass amps, and most keyboard amps, do okay as
acoustic guitar amps, but generally no better than a PA. Keyboard and bass amps tend to be heavier than
acoustic guitar amps, so you pay a penalty.
If you want to get by cheap, you might do well with an old Boss 505 acoustic effects pedal. Of all the combinations I mention, this is the only one I have not tried, but I'd like to- I suspect it is a "poor man's Fishman pre-amp." If it works, you could probably get decent results using just about any amp- electric guitar, bass, keyboard, PA. Unlikely it will be as good as a dedicated
acoustic guitar amp, though- but passable.
Cheapest and best sound would be to play through a good-quality microphone into a PA. Only drawback is you can't move around too much.
Sorry, but you can't make a silk purse from a sow's ear. (that's twice I've said that in this forum, in the last week...)