Like AnabolicDiabetic said, it varies from person to person. Personally, I don't feel its effect, unless I use 75mcg/day or more(that's for cutting), but for some guys it starts eating muscles with as low as 25mcg/day(even on bulking cycles), so:
First of all, how much steroids do you use in your cycle? If it's mild cycle and your goal is to get max of bulk out of it, don't use it at all.
If you using more then 2g of injectables or 1g of injectables and 350-700mg(depending on what kind) of orals, sure, go for 25mcg of T3.
Second, to know how you react, you have to try it, sooner or later. Not nessecery in this cycle, but you will have to learn practically, not only in theory.
Consider those points and decide.