First of all, Id suggest a GTS450 for a dual core, the CPU will hold back the 460 by a bit for some games. What do you mean by "Factory Overclocked" anyways? Is it an OEM machine?
Anyways, there are lots of monitors available in this range and I would suggest going to a local store for the convenience and the sake of shipping charges just in case you get one with a bad pixel or one you don't like, monitors are one of the more personal items when specs aren't everything.
But heres two on the egg thats pretty decent:http://www.newegg.com/Product/Product.aspx?Item=N82E16824114004http://www.newegg.com/Product/Product.aspx?Item=N82E16824005152