have you seen Boaphile's Rhinoraxx?
they look great and i've heard absolutely nothing but great reviews. their prices are decent (kind of expensive, but that's what you'll find with any pre-made rack) and they have perfected their racking systems so you don't have to worry about messing something up and having to go back and fix it in a year or two.
not to mention if you mess up a cut on a sheet of xpvc you're really screwed.
here's the goods on Rhinoraxx