Here's the lowdown:
At the office, we have a USB drive that's hooked into a Mac X Serve which is then utilized by the network IP for a NAS solution.
We're at the point where we are going to be having growing pains due to the amount of space (closing in on 1TB).
The easiest solution would be a larger USB drive (low cost).
Then there is buying an actual business-quality NAS (read: a device I can trust).
After that, the next best option I can find is putting in 2TB drives into the actual server. I'd like to avoid this due to cost ($550ish each) and quantity needed (at least 2 for RAID, then a RAID-ed backup means 4) (expensive).
I think it's high time we put a quality NAS in place, yet I can't find details on what comes highly recommended, why, and what I should really be careful about as well.
We are concerned about cost, but more so about quality and storage space.
Hope that's enough to get some recommendations or at least some sort of conversation going.
Update - Sept 4th, 2011: Ended up going with the Synology DS411+II High Performance NAS Server with Data Protection - so far, so good