Coast to coast for sure! The longer the weir the lower the sound will be for falling from the water line to the overflow (so long as you're not dropping a few feet
)
As for a totally silent operation, give this a read:
http://www.glassreef.com/basics_overflow.php
This is what I'm going to be doing in a 7' build I'm doing (overflow will only be 48" in my case due to some other design decisions).
IMHO the noise of the water over the weir will be minor, and the longer the better -- but the noise reduction to be done is in the plumbing, and a full siphon is the way to go for a drain! ...Which means you need another drain that can handle the rest which isn't under full siphon, and a third for emergency. The emergency can be skipped unless you have a wife like mine that ENJOY's the tank life, but when there is water leaking on the floor is going to be somewhere else other than helping
