It sounds like most people leave the front sway bar alone, and replace the rear if anything (that is what I did).
Increasing the front sway bar size will give you more understeer (decreasing it will give you less understeer.) As most people feel the Legacy understeers enough as it is, they leave the sway bar alone.
Of course, a bigger front bar (or smaller rear bar) will make the car less likely to fish tail, but it sounds like the ice was your real problem!