What sort of usage is your workstation going to see?
Are you in a position where you'll be working from home for example and working at the screen for prolonged periods of time? If so, I would be inclined to go for a desk clamping pole mount such as this range:
http://www.ergoindemand.com/flat_scr...r_arm_pole.htm
You'll have the flexibility of vertical adjustment without it being accidentally knocked out of the position you're comfortable with
On the other hand the gas spring arm type is particularly great for me because my work space is used primarily as a project recording studio and I've got the flexibility to move the display to suit whichever bit of kit I happen to be facing.
I got this one which is suitable for large displays but it wasn't cheap!
http://www.keytools.co.uk/product.php?productid=16306