Source vs Target upgrade

source.

I'd first build the system from the speakers back to the source (amp, pre, source). But once I was ready to make someupgrades, I start with the source and work down the second time.

With regards to a digital source, if you upgrade your downstream components to where they're too revealing, your ears will most definitely regret it. Do the digital source first; not so sure if an analog source is as critical.