I saw your post on the Hoppy/PAR thread about 4 t8s on a 20" tank. Is that the 75g tank you have pictured in your profile? The tank looks amazing.
I'm setting up a 75g and currently have 4 t8s. I was contemplating trying to upgrade the lighting, but if it's possible to get a tank that looks like yours with my current fixtures I don't see any reason to spend on better ones.