Avi's Audio Heirarchy

A practical guide for the order in which you should upgrade (or build) your AV system:

Avi's Audio Heirarchy:

1. External speakers - even a cheap soundbar - are nearly always better than the tinny ones built into your HDTV.
2. More speakers and discrete surround sound are always better than a soundbar. 
3. Subwoofers in particular make a movie sound like a movie. (Note: I have found that there is often gender bias when it comes to subs - stereotypical men want them to make things go boom, stereotypical women don't think they watch movies where it will make a difference. The men are right on this one.) 
4. Room correction - whether practical or algorithmic - is magic. You will hear a difference. In most cases, it makes a bigger difference than better speakers.
5. Better speakers make a bigger difference than better amplification or processing.
6. If you've settled all of the above, higher resolution formats can sound subtly better.
7. Of course you need functional cables, but I'm not a believer that crazy expensive cables or power conditioning provide audible improvement (it's never been proven in double blind tests. If your religion requires you to buy expensive cables or light eight candles or pray six times a day, go ahead - I do not wish to disparage your form of worship). Note: power conditioning can be essential if you live in areas with unstable electrical feeds, but that's to protect your gear. It should not provide audio improvement in areas with stable power no matter what the marketing literature says.