Recently I read something about an OS X add-on that greatly improves the audio coming out of any Mac. Freeware, as I recall, and I think it's been around for a while. But I'm drawing a blank on it. Anyone?

Google search on 'Mac improve the audio' and any variations.

Lots of various options available.

Recently I read something about an OS X add-on that greatly improves the audio coming out of any Mac. Freeware, as I recall, and I think it's been around for a while. But I'm drawing a blank on it. Anyone?

You're probably looking for the free version linked on this page.

SRS Labs :: Audio Essentials for Mac $29.99 (http://www.srslabs.com/store/store/comersus_viewItem.asp?idProduct=61)

Does a decent job, but once upon a time it used to chew up quite a few cpu cycles to do it. Not sure if the situation has improved.

Boom. It's not free, but it works well to boost volume on my MBP. I bought it a couple years back for $12 and now it's $4.99 in the app store:

Mac App Store - Boom (http://itunes.apple.com/ca/app/boom/id415312377?mt=12)

I'm not sure what the software would be though you've already been given some decent look options. Are you looking to use internal speakers or outputting to some of sound system?