If I've learned anything from this site, one person's "ace" is another's "low #3."
I think this argument strongly depends on your definition of ace.
I'd only make a move if a top tier, generational pitcher like prime Viola or Santana were somehow available. And even then, with stipulations. After all, the Mets requested a salary extension/negotation instead of just rental in Santana's case.
(They're not.)