Listen to @Taylor-Martin-Guild! The few times I have used my NH D-55, I could not hear myself, nor could anyone hear me.
The D-55 is a WONDERFUL guitar, very well rounded and can play most things...but up-front bluegrass IS NOT its thing. Funny, when you figure that a Collings D2H, same materials, KILLS in that situation. Yet, the Collings is a one-trick-pony, not subtle and not good for fingerpicking...at least, mine wasn't.
A Guild D-50 or a GAD (yes!) 50 is a much better bluegrass guitar. From my experience, a Martin HD-28 will do bluegrass and probably some other styles, but will be lacking in some. D-28 I hold away with a ten foot pole except for bluegrass. A Guild D-40 or Martin D-18 would also cover that style and probably others.
A Guild D-55 is
THE guitar if you are going to stand up at an open mic and play solo, no one will touch you! Probably would do well with old time/string band style pieces. Bluegrass AIN'T its thing. And don't EVEN THINK about plugging in if you are not the featured band