It needs no external preamp. In fact I think the sound guy turns the gain down on my guitar channel.
Tone is great.
I also have the same one installed in my D-28 and they sound almost identical. The only complaint I have is the lack of control over the volume. It will never give an accurate reproduction of a Martin with a mike at the sound hole, but it is the best amplified acoustic sound I have ever heard. It gets even better if you run the Fishman Pro EQ along with it. This also gives the much desire volume control.