The i5 with the 260 (because I don't like ATI) will do well; I'm generally not a big fan of Asus, so I'd recommend avoiding their mobos- I'd get this one instead. Either RAM will do fine; its a matter of brand preference; for $15 more, you can get Dominator, which is for all intents and purposes the second coming of God as far as RAM goes IMO- the clock speeds are a little lower, but they OC like a charm, so it won't matter. The HDD is the best on the market right now, IMO, so you're goos there. Antec makes good cases, and the 300 is a popular one, so I'd go with that. I don't really follow monitors, so I can't help there.
EDIT: If you can find an EVGA-branded 260, get it. EVGA is the best. Just remember that the Fermi chips are coming out soon...