I sold the Pre90 and bought the A90 discrete for it’s added headphone capabilities which are fantastic with my Hifiman HE 1000v2 headphones. The A90 discrete sounds a bit warmer to my ears in comparison to the Pre90. In the last couple of months I have A/B it against the Border Patrol EXT 1 and the Rogue Audio RP-7 and decided to keep the A90 Discrete in my system along with the ifi itube2. The Yaquin buffer sounded too dark, lacking details. The Jolida SSX got beat out by the itube2. I do prefer the tube buffer in front of the A90 Discrete but only by a slim margin. I could live happily with the A90 Discrete without it as well but I hear a little more presence, body and 3D soundstaging with the tube buffer in the chain.