I had sustained about 18-19% on $100SNGs for a while... I think that 25% is certainly possible, but you would have to be a VERY good player...
Honestly, if I was playing $100SNGs still, I would NOT be playing at UB... The players there are uber-tight... I would move to either Party, where the players loosen up a little, or Bodog, where they're all just nuts...