Or perhaps worded otherwise, can one apply metamagic feats (via Spell Perfection) to a Echoed copy of a spell?
No effect that allows you to reprepare or recast a spell can affect the echoed spell.
While Echoing Spell doesn't explicitly call itself out, I'd certainly consider it an effect that allows re-casting and as such can't be re-applied.
So while Spell Perfection may allow you to add a metamagic feat to the second cast, it can't be a second (or third, or fourth...) Echoing Spell because Echoing Spell forbids it.
You can't "re-echo" an echoing spell
The rules for Echoing Spell feat state:
When you cast an echoing spell, it does not disappear entirely from memory, and you can cast it one additional time during that day. No effect that allows you to reprepare or recast a spell can affect the echoed spell.
So, this feat explicitly states you cannot gain more than one recasting of the spell.
Spell Perfection may allow you to add a single metamagic effect "for free" - but you cannot apply the Echoing Spell metamagic a second time on the same "echoed spell".
Bottomline - at most, you can double your casting potential if all your spells are echoed, but you can't gain a third casting using the same slot/casting-per-day...