Your ab looks great so far!
Mind if I ask how much you have into the wood/ materials for what I see so far? I'm trying to understand the basic cost difference of buying an old cabinet vs building one.
As far as mounting angle, I figure yo can either make the screen parallel with the angle on the sides which would be more verticle or perpendicular to the angle created by the top which would be more angled. I personally would go with parallel with the front. You should measue your montior and see if one setup fits better than the other.
3 sheets of MDF @ what I think was $25 at the time.
bottle of wood glue - ~$10
2"x2"x8' wood for supports - ~$3
slot cutting bit and arbor for router ~$30
about $120 into it for far, haven't bought any buttons or joysticks yet though
thanks for the opinion, I've never built anything before so I'm very indecisive on every step because I don't know what's right versus a mistake I'll regret