Help Me Choose: Clarifying Shampoo

I need some help girls. I'm on the hunt for a miracle-working clarifying shampoo. My scalp feels like it's trapped under a layer of angry buildup! My hair gets greasy soooo fast after I wash/style it and I need something to get all the excess gunk out so I can start fresh again. I don't really use any styling products, but I still seem to have problems in this department. HELP!!!

So far, I've only found 2 highly recommended options. The first comes from the uber-beautiful Zoe. She recently blogged about the Expert Build Up Removal Shampoo from Boots (£2.93) and had fantastic results. She has amazing hair, so I would buy anything she told me to! Only problem? It's a UK-only exclusive, so I'll have to find something available stateside.



Which brings me to my second [and only realistic] option, Frederic Fekkai's Apple Cider Clarifying Shampoo ($23). It got rave reviews on Sephora.com, but it's a little pricey. I wouldn't mind paying for it if it solved all of my hair nightmares, but I don't know for sure if it will work.



Any other suggestions/advice???