I'm trying to determine the appropriate number of calories I should be eating daily.

When using the caloric needs calculators should I use my current weight (325) or my ideal weight (<200)?  

Why?

Use your present weight (lean body mass should figure into your computations).   Using current weight should give you a caloric maintenance number to maintain your current weight.  Choose a reasonable number of calories and subtract it from your maintenance number.  A pound of fat is 3500 calories so -500 calories/day should equal 1 pound of fat/week keeping activity level constant.

That is simplistic but should get you in the ballpark.  Keep in mind that you will need to recompute as you drop weight, but fat is less metabolically active than muscle so your caloric needs will not change dramatically with gradual weight loss.

Eat for the size you want to be.

Quoted: Eat for the size you want to be.

Agreed. That is about the best way to do it.

If you want to throw some numbers in there, just add up all the cals you eat in a week and see how much weight you gain or lose durring the same week. That will give you the answer. Just be sure to weigh yourself at the same time of day.