Don't buy anything until you've thoroughly checked out Kozaburo's wonderful free hair models (Digital Babes, at the lower right). You can then look to fill out your collection with a much more educated eye. I love Michael's Wedge Cut, it's beautifully made and looks good on male and females. The Wonder Wedge add-on pack adds to it's versitility, but together they're pretty pricy, and of course, majorly overexposed within the community. Vairesh keeps getting better and better - and you can buy the specific style you want for a very reasonable price. If you want to invest more, there are some good packages that offer a basic head style and lots of additional parts and morphs, so you can customize the look. A lot depends on what your end product is. For a still you can get away with arranging the hair to fit from just one perspective; for animations it's a lot trickier, most long styles just aren't up to it at this point. You end up with hair intersecting body parts, unless the morphs are very good and you tweak it frame by frame. If you are doing a still and bring it into Photoshop for postproduction, you can produce very unique and realistic (or fantastic) results. There are some good tutorials on that. I always pay attention to feedback here on hair models when they first come out. You can do a search on old messages.