Thank to both Reefgirl189 and Subman for the compliments on the stand.
Regarding what is supporting the span since the front panel is just for looks - the upper rail is in essence a 2x4 header. At a 4' span it has adequate strength to support the load and the load is transfered to the legs which the rail sits on top of. I did most of the planning in advance (my first hobby is furniture making). That being said I wasn't convinced I was right until I was forwarded the following link. It is a very close design to what I had come up with. Just to be safe I adjusted my plans and went with the recommended plan in the link.
http://reefcentral.com/forums/showthread.php?t=1169964