Wheelset Build... or Buy

I couldn't wait to make a post about my wanting to build a customized wheelset. I have a pretty good idea of what I want my wheelset to look like and a good general idea of how to get there. Although there are a few specifics I want to sort through, I know I can get what I want for around, if not under, $500. I am shooting for 50mm deep carbon rims.

A few things to keep in mind:

1. Light weight and aerodynamics are first and foremost in my mind. Efficiency is key.
2. I am not going for name brand. This means I'm not going to get Easton EC90s, Shimano Dura Ace 7801s, or even Rolf Prima Carbon TdF58s. All of those will be kept in mind while constructing my wheelset, but I'm going to Hong Kong (Ebay) for some blank carbon rims. Simple reason: Cost, folks. Cost.
3. The type of spokes are still a tossup for me. I think I am leaning a bit more toward the DT Swiss aerolite spokes (for a name-brand's sake). 
4. Probably the most important tossup I still have is between carbon tubular or carbon clincher rims. I believe they can both be fairly comparable, but as of now, I am leaning toward carbon tubular rims. Having been told I'm savvy enough to switch my respective brake pads between my current aluminum clincher and potentially full carbon rims no problem, I would have to agree and don't much care for the argument that I would have any trouble switching necessary pads in and out.
5. I haven't gotten to thinking about tires just yet.

I have already purchased the hubs I need. They are nothing special, but will get the job done. That's exactly how I am approaching this wheel building. I want everything done correctly the first time and I want a sweet go-to race wheelset. Or... I'll just buy these Matrix 50mm carbon tubulars for $635. They'll match the bike nicely, but I wouldn't mind losing a bit of that white.

Please shoot me some suggestions.