So after much research and deliberation, I finally made my purchase. I decided to configure a Synology DS211 with 1 Terabytes of storage (actually 2 x 1T Drives in a RAID1 or mirrored for redundancy). This model offered greater performance over the originally contemplated DS411j for the same cost but with less drive expandability (total 6T if required). I've spent the last several days setting up this NAS and I can comfortably say that I am VERY HAPPY with my decision.
I will not bother giving you a rundown of all the wonderful features as if you are interested in such a unit you can visit the www.synology.com
website for that. I will however let you know that the system does an excellent job of storing my 20,000+ photo library and services it out to the Internet in a very simple and efficient web interface. In the end, the unit completely met my criteria - mass photography storage, redundancy and back-up, remote access to all files, and a great digital asset management software package that performs quite acceptably over the Internet.
hope this helps anyone facing the same data storage requirements.