Alright I've had a bit more time to read the thread properly now.
There are different types of amplifiers. The type used to drive a speaker, is a power amplifier, whilst the type you need to boost the signal a bit for a sound bar is a small single amplifier.
The op-amp solution will work, but it needs to be biased to half the supply voltage and the signal coupled by capacitors.
Below are a collection of op-amp circuits showing the dual and single supply configurations. The original poster needs the top right one.
Oh I forgot to ask: is it run of a battery, which isn't powering anything else, i.e. a really smooth power supply? If so, the circuit can be simplified a bit, but I'll have to post it later, as I don't have time now.