I've been running a 23 inch Cinema HD matte display for the past 3 years and they're great. You can get them for about $350 on eBay now, too, which is where I got mine (paid $450 though).
That's the monitor I'm looking to get, the Dell Ultrasharp. A new Apple Thunderbolt monitor is out of the question at the moment.
You can get a refurbed ATD for $829 from Apple with full warranty. But that can still be far outside the budget. Even on ebay, the used ATDs seem to be in the $700+ range.
If you're OK with 1080p (1920x1080), then I recommend this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16889112058
It has the added bonus of being a passive 3D TV also, which works great with my PS3.
That's actually another one I'm looking at too. Good brand?
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Also when running an external monitor, how do you do it and have the lid closed on your MacBook Pro? And if you have Windows 7 installed via Bootcamp, does Windows 7 support this too.
If you're OK with 1080p (1920x1080), then I recommend this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16889112058
It has the added bonus of being a passive 3D TV also, which works great with my PS3.