Any good speaker should work, and 1K is plenty for such a speaker. A studio monitor speaker might work best, although the SPL is limited. You want to make sure that the level coming out of that speaker is similar to what you would get from an actual person talking in the same style. I would also agree with the above post about making sure it is recorded carefully, without too much EQ, not too close to the mic, with no effects.
Originally Posted by St_G
With those things, you should be golden.