DD2 is pretty awesome and if you like it now, you'll like if even more if you play on.
It's just beautiful and one of the best RPGs to play.
I'd be careful about the advice on DD and BD, I did not like them that much. The gameplay is just outdated and somewhat tedious, in the end, I only played DD for the story and tried to get over with it. I never managed to play more than the first hours of BD, I fear I am just five or so years too late for them.
That said, they are not expensive at all on gog.com, so feel free to give them a chance. They have been pretty good games "back then" and it's very possible you still might them.
I just want to say I'd be a bit careful with the praise of the old parts. Do not expect too much and you cannot get a bad surprise, only a good one.
Divine Gamer, I really can recommend DKS. It's great and whatever was "not that good" with it has been ironed out by the patches. There's nothing wrong with getting this game.