If you are looking for a portable device to view movies and listen to music the Kindle Fire out performs the Nook tablet in the sound department:
Sound
"There’s no comparison between the accurate, loud, and rich stereo speakers that sit on the short right side of the Kindle Fire and the distorted, clock radio-like speaker on the back of the Nook Tablet. When we tried playing music and movies on the Fire, sound was loud enough to fill a room and good enough to replace a low-end stereo. The only problem with sound on the Kindle Fire is that the device lacks physical volume buttons."
Face-Off: Amazon Kindle Fire vs. Barnes & Noble Nook Tablet
Sound
"There’s no comparison between the accurate, loud, and rich stereo speakers that sit on the short right side of the Kindle Fire and the distorted, clock radio-like speaker on the back of the Nook Tablet. When we tried playing music and movies on the Fire, sound was loud enough to fill a room and good enough to replace a low-end stereo. The only problem with sound on the Kindle Fire is that the device lacks physical volume buttons."
Face-Off: Amazon Kindle Fire vs. Barnes & Noble Nook Tablet