I'd allocate the same amount for each component including IC & speaker wire (as a group).
X for amp
X for Preamp
X for source (digital)
X for source (analog)
X for all wire
X * 2 for speakers
Etc.
X for amp
X for Preamp
X for source (digital)
X for source (analog)
X for all wire
X * 2 for speakers
Etc.