Everything seems spot on. What with your budget, that is. PSU is included with the case? I know you got budget constraints, but if you could extend your budget by 40$ and get the 110$ 7750 card, that will be the best deal. Still, if you cant, go ahead with this build. It is amazing.
I'm not opposed, exactly. Bang for the buck the Antec is better. The Corsair is a CWT made unit, and the actual max 12V is LESS than the Seasonic. It's a fine choice normally for a very low budget, but I find the Seasonic very compelling at that price.
I got a Neo Eco 620C for $30 last year, so I'm reluctant to recommend anything at a worse price point. That sentiment is, of course, ridiculous, but that's the viewpoint I'm looking at it from anyways.
To be quite honest, you're not going to make any kind of gaming PC for $400. Your hardware you listed is generally bad, sorry, but if you want to make a gaming PC with good graphics that you can actually enjoy, then I'd save up more money, at least $1000.