So I'm looking to downsize from my Mac Pro + MacBook Air setup to just the Retina MBP. Considering I'm going cross country and am going to be mobile between LA and Boston, carrying around a 75lb Mac Pro and a monitor to do video work is illogical, and now that the rMBP is out, I'm all over switching it up. My only concern is, I have so much archived data and just plain stuff, probably 3TB+ worth, and when I sell my Mac Pro, I'll be pulling at least two of my bays and keeping them with me. I also work on large projects via alternate drives. The only thing that I seem to be losing with the rMBP is the 4 swappable drive bays and I've been looking to find a solution to that. However, the big names like Drobo seem to be offering what I want at really high prices, like $400-800, which to me doesn't make too much sense. Are there any good devices that will do what I need with a fast interface without being a huge cost? I know Thunderbolt is fairly new but I haven't been following the release of these products as this will be my first computer with TB. I don't need any included storage. Thanks.