Originally Posted by YooperBrew
One pound of corn sugar will give you around 1% ABV boost, DME will give you approx .85% of a boost.
One pound won't matter much, but good beer is all about balance. You want to balance the ABV, the hops, and the malt to give a nice tasting beer.
One pound of corn sugar may just thin the body a bit and make it a bit drier, so it won't be much out of balance. As the others said, too much will cause it to be dry and cidery. A pound of DME won't make much difference either, but it would have more body and not finish as dry. Any more than a pound of either might require some tweaking of the entire recipe, so you can acheive a good balance.
So, 1/2 LB of corn sugar and 1/2 LB of DME.
One thins and one adds body, both add ABV.