Best Monitor for Macbook?

Hey guys.

I bought a Macbook Pro last month (my first Mac ever). So far my experience with it has been as good as I had hoped, but as I got the 13inch rather than the 15, I sometimes require a bigger screen.

My house is filled with external monitors, but none that really feel like they can do the operating system justice. I just used them for Windows 8.

Does anyone know any good monitors that are good enough quality for the OS and that are decent in size (I'm looking at around 25" and up) for a reasonable price? I'd like a thunderbolt, but I couldn't afford that. I'm looking at around $600 maximum.

I've been looking at the ultra wide ones made by Dell which have caught my eyes, but i'm open to suggestions :)

Thanks in advance!