The Ibanez UBs are lovely basses. Double basses they are not. However, you can string them with NS Bass/Cello strings (Omnibass). They have a rope core, the same as real DB strings. I also put my 805 through a 3 Sigma DB IR. The combination of the two gives something towards the sound of a DB but they will never sound exactly like one.
I have owned an NS CR before but I prefer the sound from the Ibanez. I just miss the 3/4 scale. They are quite light as well so useful if travelling with it. The stands are very good quality as well.