While I do not think acquiring an ace is our top priority, and maybe not even our second priority, I'd always be kicking the tires on any ace that becomes available. When I saw Quintana and Gray traded away for what I felt were relative underpays, I couldn't help but wonder "what if...".
Acquiring an ace would allow us to trade Porcello or ERod or Wright, of just keep them all. Look at the Dodgers. They stockpile starters and still end up needing another. With Pom becoming a FA after next year and Sale and Porcello the year after, you jump at an ace whenever you can.
That being said, we need a top quality clean-up hitter for 2018 to maximize our chances at a ring.