Non-Alpine hifi upgrade options (2011 123d)

[mipearson]

Still considering the Alpine retrofit, but I want to make sure there aren't other aftermarket options I can look at that wouldn't be significantly cheaper.

I'm posting here rather than the dedicated A/V forum as .AU pricing for this stuff seems to vary so much from country to country - stuff that's super-cheap in the US / UK isn't here.

Just after "better" sound rather than something that I can deafen the neighbours with. On the Forester that was as simple as installing the stock tweeter kit and a basic Sony head unit - about $300 all up, self-installed.

On the 123d I really don't want to replace the HU, so that limits my options somewhat. Also even if I get an amp & tweeters, the tweeter inserts are about $50 USD _each_. Still worth considering, though.

Relatedly, anybody know the power output of the stock head unit? Basic stereo, not the "HiFi" model.