How to finish brushed aluminium?

I'm going for a brushed aluminium look on my Leach amp that I'm dropping into a new case. Once I've brushed it, what do I use for lacquer? Would bog standard wood varnish do the trick??

What about anodising? I've heard of it but know little of it. Can one get a clear anodised finish?Is it very costly? And can anodising be done on a finished case or is it really only for sheets of aluminium?

Thanks for your advice,
Thanks Peter. I don't think I'll go with the anodised aluminium now. I've already checked out that thread and picked up some good advice so I now know how to brush the aluminium.

I'm after some short feedback on what you guys have found is the best stuff to lacquer brushed aluminium with, eg. polyurethane (as sold for painting on to wood) or a more specialised product, gloss/satin/matt? (working with metal is a novel experience for me). Or is lacquering necessary at all? The "look" I'm trying to achieve is most similar to the utilitarian lab-like Audio Research cases.