fantastic pc, its very balanced and quality components.
only problem i see is the board, why are you taking a micro atx board? they are usually more expensive and offer a very cramped up lay out. search for a good atx board to go with that pc.
also a similar card who is a littlebit stronger and a cheaper is the 7850, its operating cooler and supports dx 11.1 so overall a better decision.
if not go for the new GTX 560 ti 448 cores edition, i think it will cost the same as the 2 gigs 560 ti and will be stronger.
btw a 1080p screen is a fantastic choice! on a 20 inch screen the pixel density will be splendid and every picture will be in good quality. but just make sure you are buying a screen with good specs, high brightness and high contrast for more vivid colors and good grey to grey ratio. also a good panel type is required but not too important.