If my AGI is within the 22% bracket , does it make sense to "top-off" by taking additional discretionary IRA income up to the top of that bracket ($168400) ?

[Bsch4477]

Not if you don’t need that extra income.  You would just be paying additional taxes needlessly and you would be removing dollars from your IRA which would be earning income tax free within the IRA. 

[dmertz]

If your projections show that it makes sense to top off the 22% tax bracket but you don't need the income to cover living expenses, you would want to convert a portion of your traditional IRA to a Roth IRA rather than simply take a distribution and lose the opportunity for tax-free growth on the amount that you should have converted to Roth.