@arafiq i had the U-180 and loved it. When I had the chance to upgrade, I did it and zero regrets. Honestly, and after a bunch of bought gear through the time, probably this is the best DAC+Amp I had. I appreciate more the music instead of the gear. This is a “clichet” but in my case suits perfectly !
Never tried the U-150 but an authorized dealer (that have all gear available, New, Demo, and Used) told me that the U-180 is sonically better than the U-150 (loosing the Phono stage - that I don’t use), and the U-280 a big step above the U-180, putting the U-580 in a even higher league. This lead me to buy the I-580 and D-580, upgrading form the U-180.
I advise anyone to audition the Aavik gear with an open mind and you will very fast be surprised.
Not cheap but very very good 👍🏼