What stripe size for array?

[Rakinos]

I've picked up an Adaptec 51645, and I'm wondering what size stripe would work best. I can choose sizes between 32kb and 1024kb. I would imagine that largest would be best, as I'm generally dealing with files from a few hundred mb to a few gb in size, but I'm not sure. The array will consist of 7, 500GB wd re2s in raid 5.

Thanks in advance!