> I was thinking about using a LM358 opamp since the ~5v VCC
> is all the voltage i have. Do you think this will be enough or i will
> also need a power amplifier like lm386 ?

An op amp isn't design to drive a load like a speaker, and you'll get
only a few mA out of it. Op amps, often a paralleled quad package,
can be used to drive headphones though, as you need just a few mW

LM386 (found a few of these on mobos, fax / sound cards and they
have reasonable volume at 5V) or other amp. The TBA820 is OK
at 6V

Discrete transistor output stage, push-pull or single-ended

Use two amps in a bridge configuration

Bump up the 5V with an inverter. I've actually used an LM386 to
do this. Wired as an oscillator / tripler to make a high Vcc for a
piezo whistle. Higher Vcc widens the range of useable audio amps.
You'd have to look at what wattage is available from your 5V, or
go back a step and use the supply that the 5V comes from





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