I doubt there is any helmet out there that will give sufficient sound protection, especially wind noise on a bike without a windshield.
I have been using a Shoei Neo tech for about 2 years now, great helmet, but I still wear earplugs whenever I ride.

 

 

I run with the Shark Evo One helmet and have no complaints. The Evo One was never released in the States but the Evo One 2 has been.

 

I just bought a neotec 2 last week. Great helmet so far I have no wind noise. But then again I am on a rgs with a 14 klock works. Engine noise can be heard but it ain't too loud. I also have a built engine with D&D fatcat with loud baffle . It is quiter than my shoei gt air.

 

 

my noggin is worth $701

 

I have recently changed from an older HD Brand full face helmet to the Shoei. Very comfortable for my head shape, quiet, and easy to get on and off. Having laid down a bike in the past and lived to tell the tale, I agree with 1 2 Many, my head is worth it. Also if it keeps you and your wife on the bike longer because its comfortable and quite, then its worth the money. The built in retractable sun visor is pretty cool as well!

 

if you want it bad enough it's worth it... My current Shoei works fine for now...I am gradually getting there... The 3/4 is very comfortable...The Neotec is extremely comfortable just putting it on in the store... the drop down visor is one of my favorite because it doesn't touch my nose... As soon as I can I will have one but not now... I just don't ride as much as I did. And wearing one of those in the summer here is just plain brutal...