I just moved from a 2405FPW (PVA) to a Asus PB278Q, I have to say the Dell was an awesome monitor even now when it comes to colour, the Asus has better blacks and slightly better pixel response though not much in it, the colours are great, not sure they are as good but that might be the settings I'm using as I only just had it Saturday.
The input lag is about half what my Dell was, so that's good, just make sure your graphics card can handle what you need or want at 2560x1440, you get about a 25% performance drop in games, as it is my GTX 680 isn't enough for me.
Not sure how close the 2405 is to the 2407 but thought I'd pitch in my experience.