Source vs Target upgrade

All things being equal between source and target, which side would you upgrade first?

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.