Whatever you buy, make sure it has a lithium ion battery. There is still some very cheap junk out there with Nicad batteries which will be dead every time you take it out to use it, and the batteries will die quickly under load. Any 18 volt driver/drill with lithium ion battery will work fine for you. I used a Hitachi 18v drill for years for this purpose and it worked fine. I have power stabs now so don't use the drill any more. Any of the expensive brands, plus Craftsman, Porter Cable, Ryobi, etc, will work fine for this task. No need for an impact driver at all.
