Personally, I switched to sulfate free, silicone free and paraben free shampoos and conditioners last year and it's made a hell of a difference. Mind you, I DO have curly hair, so silicones and sulfates are bad for curly hair because they weigh the curls down and lock moisture out
If you're having problems with dryness or dullness(which may have to do with silicones or petrochemicals coating the strands), then organic may be the route for you. But to get the most benefits, before you switch, make sure to use a clarifying shampoo to start fresh and rid your hair and scalp of build-up
If build-up is your sole concern, just use a clarifying shampoo once a week or once every two weeks. You can purchase the Ion Clarifying Shampoo from Sally's for a couple of bucks and it works wonders. Clarifying shampoos remove build-up on the hair and strands but should not be used TOO often because then they could backfire and dry out hair and scalp
I like to switch up my shampoos. That seems to help a lot with everything. My experience with shampoos from like the health food store is that they don't foam up very much and I have to use more to get my hair clean. I pretty much pick shampoo based on how it smells, but sulfate-free are more gentle so I prefer them.
They don't really lather good and none of the ones I tried seemed to do much for my hair other than to clean it. The non-organic stuff seems to give me better results so I stick to using that when I want my hair to look good and use the organic products when I am not going out or doing anything that requires good-looking hair.