What's the best external monitor for an iMac?

Okay, so I borrowed my brother's monitor for a week while he was on vacation.

Long story short, I stopped using my computer for a week, because of how ugly it was. It was a Samsung 19" LCD, and I was extremely disappointed.

But recently, I've realized, I need an external display for my 21.5" iMac.

I've been looking into getting a 1080p 21.5", so they both work perfectly together.

I was looking into a few ASUS monitors, they were perfect, but I want to know if you guys have any others in mind.