I am purchasing a MacBook Pro but need a second monitor. The Thuderbolt display, although impressive, is too expensive for me.

What would be an alternative for a screen that is about 23" +?

I am not sure what spec to look for!

I am currently using a PC laptop and a 23" HP monitor but the clarity is not good (i.e. thin lines are non-existent...lack of detail).

Any thoughts?