I agree with everyone else, trying them on before purchase is essential. I used a cheaper HJC (~$120.00) for the last 8 years. It was comfortable for me and good quality for the price. Just picked up a Shoei this spring. Nearest store that carried them was 1 1/2 hours away, and it was worth the drive just to test before buying. It also vents air much better than the HJC, which is appreciated on hot days. Arai has a good reputation, but I've never found one that fit my goofy dome. Generally, the more you spend, the lighter and quieter the helmet will be. If you can swing $500 there are a lot of good options.
Consider full face over 3/4 or 1/2 shell. Safer and they keep you out of the elements a lot better on cold and rainy days. Shoei Neotec or similar is cool too, if you want the option of flipping up the face shield and visor. Talked to a guy on vacation this spring using one, and he said he'd never go back to a standard full face.
I don't like the retro-look helmets, like the Bell bubble-shield type. Form over function, and no comparison to a modern full face.