I'm using LA90 with Stealth for the couple of last days and I'm pleased.A direct connection from DAC.
I personally think the LA90's volume control is its weak link (based purely on subjective listening). For practical reasons, I use Roon's digital volume control, with the LA90 in direct mode; otherwise I'd be happy to use the DAC's vol control. I've also tried the LA90 (in direct mode) with my Pass Labs X1 preamp, and it sounded great.
I haven't kept an eye on things closely, but to date, I've not heard of a single LA90 failure/issue. FWIW, a couple of months ago, I actually bought a further two LA90s to use as monos in my second system. I haven't gotten around to setting them up yet, but am hoping to do so by the end of this week. Just an indication of how pleased I am with the LA90 .
Mani.
What I was not expecting is how smooth LA90 sounds on top.
There is zero harshness zero sibilance. And no matter how loud I listen the sound never gets distorted/collapsed or hard.
Out of curiosity have you tried using LA90 as monoblocks with your headphones?