Data isn't stored remotely. Basicaly I work on my computer and when I'm done I just want to transfer the files to the NAS system and make sure that no one can access those files even if the hard disks are retrieved.
If you are going to invest time using disk encryption then you need to to guard that investment by hardening server and clients so nobody can snoop data, get access to files in a decrypted state ("working" means there's a high probability data will reside (client-side) on disk, in memory and probably in swap as well), regularly auditing the system for intrusions or integrity problems and choosing a fitting backup strategy.
Here's some selected LQ (search) threads for you to read on disk encryption. Please read *whole* threads (except the first link). Basically these include links to HOWTO's, handle Dm-crypt and mention other stuff like Truecrypt:
Is it possible to TRULY hide a partition / data?
filesystems & encryptions
* BTW, if whole-disk encryption isn't necessary and you don't need near-military-grade encryption then there are other ways too like for instance FUSE/EncFS.