In the event that you're not a fan of Good Old Games or Impulse, you should know that you can now pick up Baldur's Gate, Baldur's Gate II, Icewind Dale, Icewind Dale II, Neverwinter Nights, and all of their expansion packs from GamersGate. Interestingly enough, you can also grab Ossian Studios' Mysteries of Westgate from them now, in case you previously purchased Neverwinter Nights 2. The pricing is very similar across the board, so I guess it really comes down to personal preference for which service earns your dollars.
Keep in mind, however, that Good Old Games is the only one offering Planescape: Torment at the moment. Perhaps there are additional hoops to jump through for that particular IE title?