Need entry level NAS recomendations

[DieCad]

I have a "Windows NT Server" domain / file / print server with 120GB storage capacity and a VXA2 tape back-up (ArcServe Back-Up for Windows NT server). The system is getting bogged down and storage space is becoming to small. We are switching over from a 2-D design environment to a 3-D design environment including simulations. File recovery is slower than I'd like. I am looking into transfering the file server responsibilities over to a NAS product. I've looked at the LinkSys EFG120 because of the gigabit ethernet capability and the expandability of the storage capacity (starts at 120GB and can grow to 480GB). I was thinking of buying two and backing up data to the second one every 12 hours, then off to a tape drive for disaster recovery & long term back-up purposes. I haven't found very many reviews on the product though and am looking for some input. I've also looked at the Fastora NAS-T2 (up to 600GB) which is more expensive. SNAPserver NAS seem to have the most possitive reviews, so maybe the 1100/250 model would be worth looking at? Is there somewhere I can look that would give me review/compare on these or some good input on what features I should be looking at? Some seem to come with software for back-up of data but I haven't been able to get a clear picture of which may be better than another. Can some back up open files while others can't? I know this is a large and loaded question but any input would be appreciated.