There really aren't a lot of choices in TB storage right now. And the ones that currently available aren't exactly what I'd consider "cost effective".
LaCie makes a dual-disk solution called the 2big Thunderbolt that currently goes up to 6TB and is RAID 0/1 switchable. Those start at a lofty $649 for 4TB. They also have a Thunderbolt variant of the Little Big Disk, but it's really not a ton of storage for video. And again, expensive (starts at $380 for only 1TB). Western Digital has a few similar products out now as well, at similar price points.
And then there's the Promise Pegasus arrays. They come in 4- or 6-drive configurations (R4 and R6, respectively) and they're expensive (over $1,000 for the 4TB R4). AFAIK, there's no way to buy an R4 or R6 chassis without drives already installed. The notable advantage with the Pegasus stuff is that it'll do the RAID-5/6 configurations that aren't possible on the dual-disk LaCie and WD offerings.
Those are really the only options available at the moment...