No thread in particular to be honest. But in X5-3 thread, people are going to recommend X5-3.
For the record, I am using a FiiO X5-2, heard all FiiO and Sony DAPs and plan to make all efforts to get a FiiO X7 next gen when it comes out.
I will recommend X5-3 if you like smooth signatures or X7 + AM 03 if you like energetic / neutral signatures with sweet mids.
X5-2 is practically solid stable, has a neutral-ish signature with sweet mids as well.
What are you looking for that doesn't let you sleep though?
X5-2 makes me happy, X5-3 would make me happy, X7 would make me really happy. If you're not happy to begin with, no DAP can brighten your day enough - happiness comes from within... The things that made me happy DAP wise were the first time I heard X7 and the first time I heard X5-3 while on tour. Also when going from Cowon J3 to X5, I was smiling for weeks and when going from X5 to X5-2 it was a really fun experience. Totally made my day better in both cases