Throw away yeast? That'd be yeast abuse!
Dry yeast have a much higher cell count than liquid which is why liquid yeast are used in starters, and from the discussions I've had and literature read, starters are not necessary or desired for dry yeast. Mr. Malty is pretty highly thought of so go with the recommended 1.5 packs and save the .5 for another time. just my 2cents.