1. They need to be calibrated...
I use a spyder three express (it is apart of their affordable range)
http://spyder.datacolor.com/product-mc-s3express.php
To learn more about colour calibration
http://www.northlight-images.co.uk/article_pages/CM_intro.html
2. Monitors can only display a limited range of colours.
Most monitors will be more than enough for most applications.
Many photographers prefer the consistency of apple monitors (because it is consistant compared to all the other brands on the market for windows.
Some of the best monitors include the
Dell UltraSharp (http://www.dell.com/content/topics/topic.aspx/global/products/landing/en/ultrasharpmonitor?c=us&l=en&cs=04)
and anything from
Eizo (http://www.eizo.com/global/)