Very happy with my ULS-15 subs that I bought new from HSU. I haven't needed service after the sale, but the service during the process was top notch.
Great service from HSU Research
Just FYI, my old HSU sub needed servicing. I emailed HSU (Steve) and got a quick response back, agreed to sent them just the amp itself and it was fixed and back in my hands in a week or so. Very fair price too. Good job HSU!