Glad you're enjoying the U-150. I love my U-280 unit -- both the integrated amp and DAC are phenomenal and the best I've heard in my system. The built-in DAC easily surpasses my previous DAC -- Defanfrips Terminator 2 by quite some margin. It's a shame that the brand flies under the radar and puts off some people because it uses class D for several models.
For fuses, best to reach out to a dealer -- I highly recommend Next Level Hifi. They are really cool folks and always willing to help even if you don't purchase from them. Good luck!