HUD with prefabs

It is now obvious to me that the way I am currently making my HUD(with GUI.DrawTexture), isn’t working. It looks very nice, but I cannot change the values via a function. The bar size simply will not update unless you hard-code the value. So I’m looking for options.
I want a box to surround the HUD, if I can change the material color of it, even better.
I have three bars: one for life, one for stamina and one for energy(magic).
There is a also a gemstone where the character name is and a circle behind it that shows the alignment of the player with color. Starts off medium gray and gets progressively lighter or darker with quests, deeds, etc.

When I instantiate a prefab-style bar, the surrounding box disappears.
Suggestions? Options? I’m open.

I use NGUI in my project and it’s easy and powerful. I have the paid version but I think you can pretty much do what you want with the free one. Take a look at UISlider.